Web Service

Adversaries may use an existing, legitimate external Web service as a means for relaying data to/from a compromised system. Popular websites and social media acting as a mechanism for C2 may give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google or Twitter, makes it easier for adversaries to hide in expected noise. Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.

Use of Web services may also protect back-end C2 infrastructure from discovery through malware binary analysis while also enabling operational resiliency (since this infrastructure may be dynamically changed).

ID: T1102
Sub-techniques:  T1102.001, T1102.002, T1102.003
Tactic: Command And Control
Platforms: Linux, Windows, macOS
Permissions Required: User
Data Sources: Host network interface, Netflow/Enclave netflow, Network protocol analysis, Packet capture, SSL/TLS inspection
Contributors: Anastasios Pingios
Version: 1.1
Created: 31 May 2017
Last Modified: 26 March 2020

Procedure Examples

Name Description
Chimera

Chimera has used Google Cloud's appspot service to host C2 servers.[1]

FIN6

FIN6 has used Pastebin and Google Storage to host content for their operations.[2]

Gamaredon Group

Gamaredon Group has used GitHub repositories for downloaders which will be obtained by the group's .NET executable on the compromised system.[3]

Inception

Inception has incorporated at least five different cloud service providers into their C2 infrastructure including CloudMe.[4][5]

Ngrok

Ngrok has been used by threat actors to proxy C2 connections to ngrok service subdomains.[6]

Rocke

Rocke has used Pastebin, Gitee, and GitLab for Command and Control.[7][8]

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.

Restrict Web-Based Content

Web proxies can be used to enforce external network communication policy that prevents use of unauthorized external services.

Detection

Host data that can relate unknown or suspicious process activity using a network connection is important to supplement any existing indicators of compromise based on malware command and control signatures and infrastructure or the presence of strong encryption. Packet capture analysis will require SSL/TLS inspection if data is encrypted. Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server). User behavior monitoring may help to detect abnormal patterns of activity.[9]

References