Uncommonly Used Port
|Uncommonly Used Port|
|Tactic||Command and Control|
|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||Netflow/Enclave netflow, Process use of network, Process monitoring|
Adversaries may conduct C2 communications over a non-standard port to bypass proxies and firewalls that have been improperly configured.
- An APT3 downloader establishes SOCKS5 connections to two separate IP addresses over TCP port 1913 and TCP port 81.1
- Some Lazarus Group malware uses a list of ordered port numbers to choose a port for C2 traffic, which includes uncommonly used ports such as 995, 1816, 465, 1521, 3306, and many others.2
- Group5 C2 servers communicated with malware over TCP 8081, 8282, and 8083.3
- A variant of ADVSTORESHELL attempts communication to the C2 server over HTTP on port 443.4
- ELMER uses HTTP over port 443 for command and control.5
- MobileOrder communicates with its C2 server over TCP port 3728.6
- A Remsec module has a default C2 port of 13000.7
Properly configure firewalls and proxies to limit outgoing traffic to only necessary ports.
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 protocol 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.8
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.8
- Moran, N., et al. (2014, November 21). Operation Double Tap. Retrieved January 14, 2016.
- Novetta Threat Research Group. (2016, February 24). Operation Blockbuster: Remote Administration Tools & Content Staging Malware Report. Retrieved March 16, 2016.
- Scott-Railton, J., et al. (2016, August 2). Group5: Syria and the Iranian Connection. Retrieved September 26, 2016.
- Bitdefender. (2015, December). APT28 Under the Scope. Retrieved February 23, 2017.
- Winters, R.. (2015, December 20). The EPS Awakens - Part 2. Retrieved January 22, 2016.
- Falcone, R. and Miller-Osborn, J.. (2016, January 24). Scarlet Mimic: Years-Long Espionage Campaign Targets Minority Activists. Retrieved February 10, 2016.
- Kaspersky Lab's Global Research & Analysis Team. (2016, August 9). The ProjectSauron APT. Technical Analysis. Retrieved August 17, 2016.
- Gardiner, J., Cova, M., Nagaraja, S. (2014, February). Command & Control Understanding, Denying and Detecting. Retrieved April 20, 2016.