Adversaries may use an existing, legitimate external Web service as a means for relaying commands to a compromised system.
These commands may also include pointers to command and control (C2) infrastructure. Adversaries may post content, known as a dead drop resolver, on Web services with embedded (and often obfuscated/encoded) domains or IP addresses. Once infected, victims will reach out to and be redirected by these resolvers.
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).
|APT12||APT12 has used blogs and WordPress for C2 infrastructure. |
|APT37||APT37 leverages social networking sites and cloud platforms (AOL, Twitter, Yandex, Mediafire, pCloud, Dropbox, and Box) for C2.  |
|BADNEWS||BADNEWS can use multiple C2 channels, including RSS feeds, Github, forums, and blogs. BADNEWS also collects C2 information via a dead drop resolver.   |
|BLACKCOFFEE||BLACKCOFFEE uses Microsoft’s TechNet Web portal to obtain a dead drop resolver containing an encoded tag with the IP address of a command and control server. It has also obfuscated its C2 traffic as normal traffic to sites such as Github.  |
|BRONZE BUTLER||BRONZE BUTLER's MSGET downloader uses a dead drop resolver to access malicious payloads. |
|CALENDAR||The CALENDAR malware communicates through the use of events in Google Calendar.  |
|Carbanak||Carbanak has used a VBScript named "ggldr" that uses Google Apps Script, Sheets, and Forms services for C2. |
|CloudDuke||One variant of CloudDuke uses a Microsoft OneDrive account to exchange commands and stolen data with its operators. |
|Comnie||Comnie uses blogs and third-party sites (GitHub, tumbler, and BlogSpot) to avoid DNS-based blocking of their communication to the command and control server. |
|CozyCar||CozyCar uses Twitter as a backup C2 channel to Twitter accounts specified in its configuration file. |
|DOGCALL||DOGCALL is capable of leveraging cloud storage APIs such as Cloud, Box, Dropbox, and Yandex for C2.  |
|Empire||Empire can use Dropbox and GitHub for C2. |
|FIN6||FIN6 has used Pastebin to host content for the operation. |
|FIN7||FIN7 used legitimate services like Google Docs, Google Scripts, and Pastebin for C2. |
|GLOOXMAIL||GLOOXMAIL communicates to servers operated by Google using the Jabber/XMPP protocol.  |
|HAMMERTOSS||The "tDiscoverer" variant of HAMMERTOSS establishes a C2 channel by downloading resources from Web services like Twitter and GitHub. HAMMERTOSS binaries contain an algorithm that generates a different Twitter handle for the malware to check for instructions every day. |
|KARAE||KARAE can use public cloud-based storage providers for command and control. |
|Kazuar||Kazuar has used compromised WordPress blogs as C2 servers. |
|Leviathan||Leviathan has received C2 instructions from user profiles created on legitimate websites such as Github and TechNet. |
|LOWBALL||LOWBALL uses the Dropbox cloud storage service for command and control. |
|Magic Hound||Magic Hound malware can use a SOAP Web service to communicate with its C2 server. |
|MiniDuke||Some MiniDuke components use Twitter to initially obtain the address of a C2 server or as a backup if no hard-coded C2 server responds.  |
|OnionDuke||OnionDuke uses Twitter as a backup C2 method. It also has a module designed to post messages to the Russian VKontakte social media site. |
|Orz||Orz has used Technet and Pastebin web pages for command and control. |
|Patchwork||Patchwork hides base64-encoded and encrypted C2 server locations in comments on legitimate websites. |
|PlugX||PlugX uses Pastebin to store C2 addresses. |
|POORAIM||POORAIM has used AOL Instant Messenger for C2. |
PowerStallion uses Microsoft OneDrive as a C2 server via a network drive mapped with
|Revenge RAT||Revenge RAT used blogpost.com as its primary command and control server during a campaign. |
|RogueRobin||RogueRobin has used Google Drive as a Command and Control channel. |
|ROKRAT||ROKRAT leverages legitimate social networking sites and cloud platforms (Twitter, Yandex, and Mediafire) for command and control communications.  |
|RTM||RTM has used an RSS feed on Livejournal to update a list of encrypted C2 server names. |
|SLOWDRIFT||SLOWDRIFT uses cloud based services for C2. |
|Twitoor||Twitoor uses Twitter for command and control. |
|UBoatRAT||UBoatRAT has used GitHub and a public blog service in Hong Kong for C2 communications. |
|Xbash||Xbash can obtain a webpage hosted on Pastebin to update its C2 domain list. |
|yty||yty communicates to the C2 server by retrieving a Google Doc. |
|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.|
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. Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used. 
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