To disguise the source of malicious traffic, adversaries may chain together multiple proxies. Typically, a defender will be able to identify the last proxy traffic traversed before it enters their network; the defender may or may not be able to identify any previous proxies before the last-hop proxy. This technique makes identifying the original source of the malicious traffic even more difficult by requiring the defender to trace malicious traffic through several proxies to identify its source.
A backdoor used by APT29 created a Tor hidden service to forward traffic from the Tor client to local ports 3389 (RDP), 139 (Netbios), and 445 (SMB) enabling full remote access from outside the network.
|Filter Network Traffic||
Traffic to known anonymity networks and C2 infrastructure can be blocked through the use of network black and white lists. It should be noted that this kind of blocking may be circumvented by other techniques like Domain Fronting.
When observing use of Multi-hop proxies, network data from the actual command and control servers could allow correlating incoming and outgoing flows to trace malicious traffic back to its source. Multi-hop proxies can also be detected by alerting on traffic to known anonymity networks (such as Tor) or known adversary infrastructure that uses this technique.
- Roger Dingledine, Nick Mathewson and Paul Syverson. (2004). Tor: The Second-Generation Onion Router. Retrieved December 21, 2017.
- Patrick Wardle. (n.d.). Mac Malware of 2017. Retrieved September 21, 2018.
- Cherepanov, A. (2018, October). GREYENERGY A successor to BlackEnergy. Retrieved November 15, 2018.
- Patrick Wardle. (2017, January 1). Mac Malware of 2016. Retrieved September 21, 2018.
- Counter Threat Unit Research Team. (2017, May 18). WCry Ransomware Analysis. Retrieved March 26, 2019.
- NJCCIC. (2016, September 27). Ursnif. Retrieved June 4, 2019.
- Proofpoint Staff. (2016, August 25). Nightmare on Tor Street: Ursnif variant Dreambot adds Tor functionality. Retrieved June 5, 2019.
- Dunwoody, M. and Carr, N.. (2016, September 27). No Easy Breach DerbyCon 2016. Retrieved October 4, 2016.
- Vengerik, B. et al.. (2014, December 5). Hacking the Street? FIN4 Likely Playing the Market. Retrieved December 17, 2018.