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Data Encoding
Sub-techniques (2)
Adversaries may encode data to make the content of command and control traffic more difficult to detect. Command and control (C2) information can be encoded using a standard data encoding system. Use of data encoding may adhere to existing protocol specifications and includes use of ASCII, Unicode, Base64, MIME, or other binary-to-text and character encoding systems.[1] [2] Some data encoding systems may also result in data compression, such as gzip.
Procedure Examples
| Name | Description |
|---|---|
| BADNEWS |
After encrypting C2 data, BADNEWS converts it into a hexadecimal representation and then encodes it into base64.[5] |
| H1N1 |
H1N1 obfuscates C2 traffic with an altered version of base64.[4] |
| Linux Rabbit |
Linux Rabbit sends the payload from the C2 server as an encoded URL parameter. [6] |
| Ursnif |
Mitigations
| Mitigation | Description |
|---|---|
| Network Intrusion Prevention |
Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware can be used to mitigate activity at the network level. Signatures are often for unique indicators within protocols and may be based on the specific obfuscation technique used by a particular adversary or tool, and will likely be different across various malware families and versions. Adversaries will likely change tool C2 signatures over time or construct protocols in such a way as to avoid detection by common defensive tools. [3] |
Detection
Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). Processes utilizing the network that do not normally have network communication or have never been seen before are suspicious. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used. [3]
References
- Wikipedia. (2016, December 26). Binary-to-text encoding. Retrieved March 1, 2017.
- Wikipedia. (2017, February 19). Character Encoding. Retrieved March 1, 2017.
- Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.
- Reynolds, J.. (2016, September 14). H1N1: Technical analysis reveals new capabilities – part 2. Retrieved September 26, 2016.
- Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
- Anomali Labs. (2018, December 6). Pulling Linux Rabbit/Rabbot Malware Out of a Hat. Retrieved March 4, 2019.
- Proofpoint Staff. (2016, August 25). Nightmare on Tor Street: Ursnif variant Dreambot adds Tor functionality. Retrieved June 5, 2019.