File Deletion

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File Deletion
Technique
ID T1107
Tactic Defense Evasion
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1, Linux
Permissions Required User
Data Sources File monitoring, Binary file metadata, Process command-line parameters
Defense Bypassed Host forensic analysis
Contributors Walker Johnson

Malware, tools, or other non-native files dropped or created on a system by an adversary may leave traces behind as to what was done within a network and how. Adversaries may remove these files over the course of an intrusion to keep their footprint low or remove them at the end as part of the post-intrusion cleanup process.

There are tools available from the host operating system to perform cleanup, but adversaries may use other tools as well. Examples include native cmd functions such as DEL, secure deletion tools such as Windows Sysinternals SDelete, or other third-party file deletion tools.1

Examples

  • APT18 actors deleted tools and batch files from victim systems.2
  • Lazarus Group malware contains "suicide scripts" to delete malware binaries from the victim. It also uses secure file deletion to delete files from the victim.3
  • Malware used by Group5 is capable of remotely deleting files from victims.4
  • Derusbi is capable of deleting files. It has been observed loading a Linux Kernel Module (LKM) and then deleting it from the hard disk as well as overwriting the data with null bytes.5
  • gh0st RAT is able to delete files.6
  • The JHUHUGIT dropper deletes itself from the victim.7
  • ADVSTORESHELL can delete files and directories.8
  • SeaDuke can securely delete files, including deleting itself from the victim.9
  • pngdowner deletes content from C2 communications that was saved to the user's temporary directory.10
  • BLACKCOFFEE has the capability to delete files.11
  • HTTPBrowser deletes its original installer file once installation is complete.12
  • Some Sakula samples use cmd.exe to delete temporary files.13
  • Misdat is capable of deleting the backdoor file.14
  • Hi-Zor deletes its RAT installer file as it executes its DLL payload file.15
  • BlackEnergy 2 contains a "Destroy" plug-in that destroys data stored on victim hard drives by overwriting file contents.16
  • Backdoor.Oldrea contains a cleanup module that removes traces of itself from the victim.17
  • cmd can be used to delete files from the file system.18
  • Recent versions of Cherry Picker delete files and registry keys created by the malware.19
  • Remsec is capable of deleting files on the victim.2021 It also securely removes itself after collecting and exfiltrating data.22
  • BBSRAT can delete files and directories.23
  • H1N1 deletes shadow copies from the victim.24
  • USBStealer has several commands to delete files associated with the malware from the victim.25
  • PowerDuke has a command to write random data across a file and delete it.26
  • Shamoon attempts to overwrite operating system files with image files.2728
  • Pteranodon can delete files that may interfere with it executing. It also can delete temporary files and itself after the initial script executes.29
  • RTM can delete all files created during its execution.30
  • MoonWind can delete itself or specified files.31

Mitigation

Identify unnecessary system utilities, third-party tools, or potentially malicious software that may be used to delete files, and audit and/or block them by using whitelisting32 tools like AppLocker3334 or Software Restriction Policies35 where appropriate.36

Detection

It may be uncommon for events related to benign command-line functions such as DEL or third-party utilities or tools to be found in an environment, depending on the user base and how systems are typically used. Monitoring for command-line deletion functions to correlate with binaries or other files that an adversary may drop and remove may lead to detection of malicious activity. Another good practice is monitoring for known deletion and secure deletion tools that are not already on systems within an enterprise network that an adversary could introduce. Some monitoring tools may collect command-line arguments, but may not capture DEL commands since DEL is a native function within cmd.exe.

References

  1. ^  Wilhoit, K. (2013, March 4). In-Depth Look: APT Attack Tools of the Trade. Retrieved December 2, 2015.
  2. ^  Carvey, H.. (2014, September 2). Where you AT?: Indicators of lateral movement using at.exe on Windows 7 systems. Retrieved January 25, 2016.
  3. ^  Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Unraveling the Long Thread of the Sony Attack. Retrieved February 25, 2016.
  4. ^  Scott-Railton, J., et al. (2016, August 2). Group5: Syria and the Iranian Connection. Retrieved September 26, 2016.
  5. ^  Fidelis Cybersecurity. (2016, February 29). The Turbo Campaign, Featuring Derusbi for 64-bit Linux. Retrieved March 2, 2016.
  6. ^  FireEye Threat Intelligence. (2015, July 13). Demonstrating Hustle, Chinese APT Groups Quickly Use Zero-Day Vulnerability (CVE-2015-5119) Following Hacking Team Leak. Retrieved January 25, 2016.
  7. ^  ESET. (2016, October). En Route with Sednit - Part 1: Approaching the Target. Retrieved November 8, 2016.
  8. ^  ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016.
  9. ^  Symantec Security Response. (2015, July 13). “Forkmeiamfamous”: Seaduke, latest weapon in the Duke armory. Retrieved July 22, 2015.
  10. ^  Crowdstrike Global Intelligence Team. (2014, June 9). CrowdStrike Intelligence Report: Putter Panda. Retrieved January 22, 2016.
  11. ^  FireEye Labs/FireEye Threat Intelligence. (2015, May 14). Hiding in Plain Sight: FireEye and Microsoft Expose Obfuscation Tactic. Retrieved January 22, 2016.
  12. ^  Desai, D.. (2015, August 14). Chinese cyber espionage APT group leveraging recently leaked Hacking Team exploits to target a Financial Services Firm. Retrieved January 26, 2016.
  13. ^  Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, July 30). Sakula Malware Family. Retrieved January 26, 2016.
  14. ^  Gross, J. (2016, February 23). Operation Dust Storm. Retrieved February 25, 2016.
  15. ^  Fidelis Cybersecurity. (2015, December 16). Fidelis Threat Advisory #1020: Dissecting the Malware Involved in the INOCNATION Campaign. Retrieved March 24, 2016.
  16. ^  Baumgartner, K. and Garnaeva, M.. (2015, February 17). BE2 extraordinary plugins, Siemens targeting, dev fails. Retrieved March 24, 2016.
  17. ^  Symantec Security Response. (2014, July 7). Dragonfly: Cyberespionage Attacks Against Energy Suppliers. Retrieved April 8, 2016.
  18. ^  Microsoft. (n.d.). Del. Retrieved April 22, 2016.
  1. ^  Merritt, E.. (2015, November 16). Shining the Spotlight on Cherry Picker PoS Malware. Retrieved April 20, 2016.
  2. ^  Symantec Security Response. (2016, August 8). Backdoor.Remsec indicators of compromise. Retrieved August 17, 2016.
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