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, Windows 10, MacOS, OS X
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
  • APT28 has deleted files from the system via the NSFileManager:removeFileAtPath method 3.
  • APT32 has cleared select event log entries.4
  • FIN10 has used batch scripts and scheduled tasks to delete critical system files.5
  • Malware used by Group5 is capable of remotely deleting files from victims.6
  • 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.7
  • Threat Group-3390 has deleted existing logs and exfiltrated file archives from a victim.8
  • ADVSTORESHELL can delete files and directories.9
  • BBSRAT can delete files and directories.10
  • BLACKCOFFEE has the capability to delete files.11
  • Backdoor.Oldrea contains a cleanup module that removes traces of itself from the victim.12
  • BlackEnergy 2 contains a "Destroy" plug-in that destroys data stored on victim hard drives by overwriting file contents.13
  • Recent versions of Cherry Picker delete files and registry keys created by the malware.14
  • 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.15
  • H1N1 deletes shadow copies from the victim.16
  • HALFBAKED can delete a specified file.17
  • HTTPBrowser deletes its original installer file once installation is complete.18
  • Hi-Zor deletes its RAT installer file as it executes its DLL payload file.19
  • The JHUHUGIT dropper deletes itself from the victim.20
  • The Komplex trojan supports file deletion 21
  • Misdat is capable of deleting the backdoor file.22
  • MoonWind can delete itself or specified files.23
  • PowerDuke has a command to write random data across a file and delete it.24
  • Pteranodon can delete files that may interfere with it executing. It also can delete temporary files and itself after the initial script executes.25
  • RTM can delete all files created during its execution.26
  • RedLeaves can delete specified files.27
  • Remsec is capable of deleting files on the victim.2829 It also securely removes itself after collecting and exfiltrating data.30
  • Some Sakula samples use cmd.exe to delete temporary files.31
  • SeaDuke can securely delete files, including deleting itself from the victim.32
  • Shamoon attempts to overwrite operating system files with image files.3334
  • USBStealer has several commands to delete files associated with the malware from the victim.35
  • WINDSHIELD is capable of file deletion along with other file system interaction.4
  • XAgentOSX contains the deletFileFromPath function to delete a specified file using the NSFileManager:removeFileAtPath method.3
  • cmd can be used to delete files from the file system.36
  • gh0st RAT is able to delete files.37
  • pngdowner deletes content from C2 communications that was saved to the user's temporary directory.38

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 whitelisting39 tools like AppLocker4041 or Software Restriction Policies42 where appropriate.43

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

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  4. a b  Carr, N.. (2017, May 14). Cyber Espionage is Alive and Well: APT32 and the Threat to Global Corporations. Retrieved June 18, 2017.
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  12. ^  Symantec Security Response. (2014, July 7). Dragonfly: Cyberespionage Attacks Against Energy Suppliers. Retrieved April 8, 2016.
  13. ^  Baumgartner, K. and Garnaeva, M.. (2015, February 17). BE2 extraordinary plugins, Siemens targeting, dev fails. Retrieved March 24, 2016.
  14. ^  Merritt, E.. (2015, November 16). Shining the Spotlight on Cherry Picker PoS Malware. Retrieved April 20, 2016.
  15. ^  Fidelis Cybersecurity. (2016, February 29). The Turbo Campaign, Featuring Derusbi for 64-bit Linux. Retrieved March 2, 2016.
  16. ^  Reynolds, J.. (2016, September 14). H1N1: Technical analysis reveals new capabilities – part 2. Retrieved September 26, 2016.
  17. ^  Carr, N., et al. (2017, April 24). FIN7 Evolution and the Phishing LNK. Retrieved April 24, 2017.
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