External Remote Services

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External Remote Services
ID T1133
Tactic Persistence
Platform Windows
Permissions Required User
Data Sources Authentication logs
Contributors Daniel Oakley, Travis Smith, Tripwire

Remote services such as VPNs, Citrix, and other access mechanisms allow users to connect to internal enterprise network resources from external locations. There are often remote service gateways that manage connections and credential authentication for these services. Services such as Windows Remote Management can also be used externally.

Adversaries may use remote services to access and persist within a network.1 Access to Valid Accounts to use the service is often a requirement, which could be obtained through credential pharming or by obtaining the credentials from users after compromising the enterprise network. Access to remote services may be used as part of Redundant Access during an operation.


  • APT18 actors leverage legitimate credentials to log into external remote services.2
  • APT34 uses remote services such as VPN, Citrix, or OWA to persist in an environment.3
  • Dragonfly used remote access services, including VPN and Outlook Web Access (OWA).4
  • FIN5 has used legitimate VPN, RDP, Citrix, or VNC credentials to maintain access to a victim environment.567
  • Threat Group-3390 actors look for and use VPN profiles during an operation to access the network using external VPN services.8


Limit access to remote services through centrally managed concentrators such as VPNs and other managed remote access systems. Deny direct remote access to internal systems through uses of network proxies, gateways, and firewalls as appropriate. Disable or block services such as Windows Remote Management can be used externally. Use strong two-factor or multi-factor authentication for remote service accounts to mitigate an adversary's ability to leverage stolen credentials, but be aware of Two-Factor Authentication Interception techniques for some two-factor authentication implementations.


Follow best practices for detecting adversary use of Valid Accounts for authenticating to remote services. Collect authentication logs and analyze for unusual access patterns, windows of activity, and access outside of normal business hours.