I spend a lot of my red time in the Access Manager role. This is the person on a red team who manages callbacks for the red cell. Sometimes, I like to grab a Beacon and drive around a network. It’s important to get out once in a while and enjoy what’s there. Cobalt Strike 2.5 is all about cruising around networks.
This release adds native lateral movement options to Beacon. Use the psexec_psh, winrm, and wmi commands to deliver a Beacon to a target using PowerShell to avoid touching disk. For you old school types, a psexec command is available to deliver a Beacon to a target with an Artifact Kit service executable.
You’ll likely notice that Cobalt Strike’s lateral movement options do not accept credentials, hashes, or other credential material. Keeping with Cobalt Strike’s operating philosophy, these lateral movement options rely on what’s in your access token to authenticate with a remote system. If you want to pass-the-hash with Beacon; use mimikatz to create a token that passes your hash. If you need to pass credentials, use Cobalt Strike 2.5’s make_token command to create a token to pass the credentials you provide.
Named Pipe Stager
Cobalt Strike’s best payload for lateral movement is the SMB Beacon. This Beacon uses a named pipe to receive commands from and relay output through another Beacon. A named pipe is an inter-process communication mechanism on Windows. Named pipes also work host-to-host to allow two programs to communicate with each other over the network. This traffic is encapsulated in the SMB protocol.
The SMB beacon is awesome but it had a weakness. It’s too big to use with attacks like psexec_psh. Cobalt Strike 2.5 solves this problem with its named pipe stager. This tiny stager delivers the SMB Beacon to a remote target over a named pipe. This stager works well with Beacon’s new lateral movement options that don’t touch disk. This is quite an upgrade from the previous best practices.
Red Teams pivot, not just host-to-host, but process-to-process on the same host. This need is usually driven by egress and evasion concerns. A process run as an unprivileged user may have the ability to egress. As soon as you elevate, you may run into difficulties if that elevated process can’t communicate out.
Cobalt Strike 2.5 uses the SMB Beacon to help with this problem. Beacon features to include its Bypass UAC attack and new spawnas command [use credentials to spawn a payload; without touching disk] accept the SMB Beacon as a target payload. This greatly improves Cobalt Strike’s options to work through one egress channel.
Reverse Port Forwards
Cobalt Strike 2.5 also adds reverse port forwarding. Beacon’s new rportfwd command will bind a port of your choice on a compromised target. When someone connects to this port, Cobalt Strike’s team server will establish a connection to a forward host and port of your choosing. It will then relay traffic, via Beacon, between this new connection and the client connected to your Beacon. Now, you can use compromised systems as arbitrary redirectors. ☺