Obfuscated Files or Information

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Obfuscated Files or Information
ID T1027
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
Data Sources Network protocol analysis, Process use of network, Binary file metadata, File monitoring, Malware reverse engineering
Defense Bypassed Host forensic analysis, Signature-based detection, Host intrusion prevention systems

Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system.


  • Droppers used by Putter Panda use RC4 or a 16-byte XOR key consisting of the bytes 0xA0 – 0xAF to obfuscate payloads.1
  • Dust Storm has encoded payloads with a single-byte XOR, both skipping the key itself and zeroing in an attempt to avoid exposing the key.2
  • Lazarus Group malware uses multiple types of encryption and encoding in its malware files, including AES, Caracachs, RC4, basic XOR with constant 0xA7, and other techniques.345
  • Group5 disguised its malicious binaries with several layers of obfuscation, including encrypting the files.6
  • Many strings in JHUHUGIT are obfuscated with a XOR algorithm.78
  • Most of the strings in ADVSTORESHELL are encrypted with an XOR-based algorithm; some strings are also encrypted with 3DES and reversed. API function names are also reversed, presumably to avoid detection in memory.9
  • The payload of CozyCar is encrypted with simple XOR with a rotating key. The CozyCar configuration file has been encrypted with RC4 keys.10
  • The DustySky dropper uses a function to obfuscate the name of functions and other parts of the malware.11
  • SHOTPUT is obscured using XOR encoding and appended to a valid GIF file.1213
  • HTTPBrowser's code may be obfuscated through structured exception handling and return-oriented programming.14
  • Sakula uses single-byte XOR obfuscation to obfuscate many of its files.15
  • Elise encrypts several of its files, including configuration files.16
  • Variants of Emissary encrypt payloads using various XOR ciphers, as well as a custom algorithm that uses the "srand" and "rand" functions.1718
  • Hi-Zor uses various XOR techniques to obfuscate its components.19
  • Some resources in Prikormka are encrypted with a simple XOR operation or encoded with Base64.20
  • A version of XTunnel introduced in July 2015 obfuscated the binary using opaque predicates and other techniques in a likely attempt to obfuscate it and bypass security products.21
  • Pisloader obfuscates files by splitting strings into smaller sub-strings and including "garbage" strings that are never used. The malware also uses return-oriented programming (ROP) technique and single-byte XOR to obfuscate data.22
  • Some data in Remsec is encrypted using RC5 in CBC mode, AES-CBC with a hardcoded key, RC4, or Salsa20. Some data is also base64-encoded.2324
  • TINYTYPHON has used XOR with 0x90 to obfuscate its configuration file.25
  • H1N1 uses multiple techniques to obfuscate strings, including XOR.26
  • Most strings in USBStealer are encrypted using 3DES and XOR and reversed.27
  • CORESHELL obfuscates strings using a custom stream cipher.28
  • OLDBAIT obfuscates internal strings and unpacks them at startup.28
  • PowerDuke uses an alternate data stream (ADS) PNG file to hide and encrypt itself using Tiny Encryption Algorithm (TEA).29
  • Shamoon contains base64-encoded strings.30


Detection of file obfuscation is difficult unless artifacts are left behind by the obfuscation process that are uniquely detectable with a signature. If detection of the obfuscation itself is not possible, it may be possible to detect the malicious activity that caused the obfuscated file (for example, the method that was used to write, read, or modify the file on the file system).


  1. ^  Crowdstrike Global Intelligence Team. (2014, June 9). CrowdStrike Intelligence Report: Putter Panda. Retrieved January 22, 2016.
  2. ^  Gross, J. (2016, February 23). Operation Dust Storm. Retrieved February 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. ^  Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Loaders, Installers and Uninstallers Report. Retrieved March 2, 2016.
  5. ^  Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Remote Administration Tools & Content Staging Malware Report. Retrieved March 16, 2016.
  6. ^  Scott-Railton, J., et al. (2016, August 2). Group5: Syria and the Iranian Connection. Retrieved September 26, 2016.
  7. ^  F-Secure. (2015, September 8). Sofacy Recycles Carberp and Metasploit Code. Retrieved August 3, 2016.
  8. ^  ESET. (2016, October). En Route with Sednit - Part 1: Approaching the Target. Retrieved November 8, 2016.
  9. ^  Kaspersky Lab's Global Research and Analysis Team. (2015, December 4). Sofacy APT hits high profile targets with updated toolset. Retrieved December 10, 2015.
  10. ^  F-Secure Labs. (2015, April 22). CozyDuke: Malware Analysis. Retrieved December 10, 2015.
  11. ^  ClearSky. (2016, January 7). Operation DustySky. Retrieved January 8, 2016.
  12. ^  Eng, E., Caselden, D.. (2015, June 23). Operation Clandestine Wolf – Adobe Flash Zero-Day in APT3 Phishing Campaign. Retrieved January 14, 2016.
  13. ^  Falcone, R. and Wartell, R.. (2015, July 27). Observations on CVE-2015-3113, Prior Zero-Days and the Pirpi Payload. Retrieved January 22, 2016.
  14. ^  Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, August 5). Threat Group-3390 Targets Organizations for Cyberespionage. Retrieved January 25, 2016.
  15. ^  Dell SecureWorks Counter Threat Unit Threat Intelligence. (2015, July 30). Sakula Malware Family. Retrieved January 26, 2016.
  1. ^  Falcone, R., et al.. (2015, June 16). Operation Lotus Blossom. Retrieved February 15, 2016.
  2. ^  Falcone, R. and Miller-Osborn, J.. (2015, December 18). Attack on French Diplomat Linked to Operation Lotus Blossom. Retrieved February 15, 2016.
  3. ^  Falcone, R. and Miller-Osborn, J.. (2016, February 3). Emissary Trojan Changelog: Did Operation Lotus Blossom Cause It to Evolve?. Retrieved February 15, 2016.
  4. ^  Fidelis Cybersecurity. (2015, December 16). Fidelis Threat Advisory #1020: Dissecting the Malware Involved in the INOCNATION Campaign. Retrieved March 24, 2016.
  5. ^  Cherepanov, A.. (2016, May 17). Operation Groundbait: Analysis of a surveillance toolkit. Retrieved May 18, 2016.
  6. ^  ESET. (2016, October). En Route with Sednit - Part 2: Observing the Comings and Goings. Retrieved November 21, 2016.
  7. ^  Grunzweig, J., et al. (2016, May 24). New Wekby Attacks Use DNS Requests As Command and Control Mechanism. Retrieved August 17, 2016.
  8. ^  Symantec Security Response. (2016, August 8). Backdoor.Remsec indicators of compromise. Retrieved August 17, 2016.
  9. ^  Kaspersky Lab's Global Research & Analysis Team. (2016, August 9). The ProjectSauron APT. Technical Analysis. Retrieved August 17, 2016.
  10. ^  Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
  11. ^  Reynolds, J.. (2016, September 13). H1N1: Technical analysis reveals new capabilities. Retrieved September 26, 2016.
  12. ^  Calvet, J. (2014, November 11). Sednit Espionage Group Attacking Air-Gapped Networks. Retrieved January 4, 2017.
  13. a b  FireEye. (2015). APT28: A WINDOW INTO RUSSIA’S CYBER ESPIONAGE OPERATIONS?. Retrieved August 19, 2015.
  14. ^  Adair, S.. (2016, November 9). PowerDuke: Widespread Post-Election Spear Phishing Campaigns Targeting Think Tanks and NGOs. Retrieved January 11, 2017.
  15. ^  Falcone, R.. (2016, November 30). Shamoon 2: Return of the Disttrack Wiper. Retrieved January 11, 2017.