Redundant Access
**This technique has been deprecated. Please use Create Account, Web Shell, and External Remote Services where appropriate.** Adversaries may use more than one remote access tool with varying command and control protocols or credentialed access to remote services so they can maintain access if an access mechanism is detected or mitigated. If one type of tool is detected and blocked or removed as a response but the organization did not gain a full understanding of the adversary's tools and access, then the adversary will be able to retain access to the network. Adversaries may also attempt to gain access to Valid Accounts to use External Remote Services such as external VPNs as a way to maintain access despite interruptions to remote access tools deployed within a target network.(Citation: Mandiant APT1) Adversaries may also retain access through cloud-based infrastructure and applications. Use of a Web Shell is one such way to maintain access to a network through an externally accessible Web server.
Mitigations |
|
| Mitigation | Description |
|---|---|
| Network Intrusion Prevention |
Use intrusion detection signatures to block traffic at network boundaries. |
| Redundant Access Mitigation |
Identify and block potentially malicious software that may be used as a remote access tool, and audit and/or block it by using whitelisting (Citation: Beechey 2010) tools, like AppLocker, (Citation: Windows Commands JPCERT) (Citation: NSA MS AppLocker) or Software Restriction Policies (Citation: Corio 2008) where appropriate. (Citation: TechNet Applocker vs SRP) 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 will be different across various malware families and versions. Adversaries will likely change tool signatures over time or construct protocols in such a way as to avoid detection by common defensive tools. (Citation: University of Birmingham C2) |
Detection
Existing methods of detecting remote access tools are helpful. Backup remote access tools or other access points may not have established command and control channels open during an intrusion, so the volume of data transferred may not be as high as the primary channel unless access is lost. Detection of tools based on beacon traffic, Command and Control protocol, or adversary infrastructure require prior threat intelligence on tools, IP addresses, and/or domains the adversary may use, along with the ability to detect use at the network boundary. Prior knowledge of indicators of compromise may also help detect adversary tools at the endpoint if tools are available to scan for those indicators. If an intrusion is in progress and sufficient endpoint data or decoded command and control traffic is collected, then defenders will likely be able to detect additional tools dropped as the adversary is conducting the operation. For alternative access using externally accessible VPNs or remote services, follow detection recommendations under Valid Accounts and External Remote Services to collect account use information.
Связанные риски
Каталоги
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