Reverse Shell Created via Named Pipeedit
Identifies a reverse shell via the abuse of named pipes on Linux with the help of OpenSSL or Netcat. First in, first out (FIFO) files are special files for reading and writing to by Linux processes. For this to work, a named pipe is created and passed to a Linux shell where the use of a network connection tool such as Netcat or OpenSSL has been established. The stdout and stderr are captured in the named pipe from the network connection and passed back to the shell for execution.
Rule type: eql
Rule indices:
- auditbeat-*
- logs-endpoint.events.*
Severity: medium
Risk score: 47
Runs every: 5 minutes
Searches indices from: now-9m (Date Math format, see also Additional look-back time)
Maximum alerts per execution: 100
References:
Tags:
- Elastic
- Host
- Linux
- Threat Detection
- Execution
- Investigation Guide
Version: 1
Added (Elastic Stack release): 8.6.0
Rule authors: Elastic
Rule license: Elastic License v2
Potential false positivesedit
Netcat and OpenSSL are common tools used for establishing network connections and creating encryption keys. While they are popular, capturing the stdout and stderr in a named pipe pointed to a shell is anomalous.
Rule queryedit
sequence by host.id with maxspan = 5s [process where event.type ==
"start" and process.executable : ("/usr/bin/mkfifo","/usr/bin/mknod")
and process.args:("/tmp/*","$*")] [process where
process.executable : ("/bin/sh","/bin/bash") and process.args:("-i")
or (process.executable: ("/usr/bin/openssl") and process.args:
("-connect"))] [process where (process.name:("nc","ncat","netcat",
"netcat.openbsd","netcat.traditional") or
(process.name: "openssl" and process.executable: "/usr/bin/openssl"))]
Threat mappingedit
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
-
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/