System Network Connections Discovery

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System Network Connections Discovery
Technique
ID T1049
Tactic Discovery
Platform Windows Server 2003, Windows Server 2008, Windows Server 2012, Windows XP, Windows 7, Windows 8, Windows Server 2003 R2, Windows Server 2008 R2, Windows Server 2012 R2, Windows Vista, Windows 8.1, Linux, Windows 10, MacOS, OS X
Permissions Required User, Administrator
Data Sources Process command-line parameters, Process monitoring

Adversaries may attempt to get a listing of network connections to or from the compromised system they are currently accessing or from remote systems by querying for information over the network.

Windows

Utilities and commands that acquire this information include netstat, "net use," and "net session" with Net.

Mac and Linux

In Mac and Linux, netstat and lsof can be used to list current connections. who -a and w can be used to show which users are currently logged in, similar to "net session".

Examples

  • Ke3chang performs local network connection discovery using netstat -ano commands.1
  • Poseidon Group obtains and saves information about victim network interfaces and addresses.2
  • Threat Group-3390 has used net use to conduct internal discovery of systems. The group has also used quser.exe to identify existing RDP sessions on a victim.3
  • Turla surveys a system upon check-in to discover active local network connections using the netstat -an, net use, net file, and net session commands.4
  • admin@338 actors used the following command following exploitation of a machine with LOWBALL malware to display network connections: netstat -ano >> %temp%\download5
  • menuPass has used net use to conduct connectivity checks to machines.6
  • BlackEnergy has gathered information about local network connections using netstat.78
  • The discovery modules used with Duqu can collect information on network connections.9
  • Commands such as net use and net session can be used in Net to gather information about network connections from a particular host.10
  • RedLeaves can enumerate drives and Remote Desktop sessions.11
  • Remsec can obtain a list of active connections and open ports.12
  • SHOTPUT uses netstat to list TCP connection status.13
  • Sykipot may use netstat -ano to display active network connections.14
  • nbtstat can be used to discover current NetBIOS sessions.
  • netstat can be used to enumerate local network connections, including active TCP connections and other network statistics.15

Mitigation

Identify unnecessary system utilities or potentially malicious software that may be used to acquire information about network connections, and audit and/or block them by using whitelisting16 tools, like AppLocker,1718 or Software Restriction Policies19 where appropriate.20

Detection

System and network discovery techniques normally occur throughout an operation as an adversary learns the environment. Data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as Lateral Movement, based on the information obtained.

Monitor processes and command-line arguments for actions that could be taken to gather system and network information. Remote access tools with built-in features may interact directly with the Windows API to gather information. Information may also be acquired through Windows system management tools such as Windows Management Instrumentation and PowerShell.

References