The hypothesis is that an adversary may be using a compromised DropBear SSH server with a known backdoor password to maintain persistent access within a network. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify potential long-term persistence mechanisms and mitigate the risk of unauthorized access.
YARA Rule
rule BlackEnergy_BackdoorPass_DropBear_SSH
{
meta:
description = "Detects the password of the backdoored DropBear SSH Server - BlackEnergy"
author = "Florian Roth"
reference = "http://feedproxy.google.com/~r/eset/blog/~3/BXJbnGSvEFc/"
date = "2016-01-03"
hash = "0969daac4adc84ab7b50d4f9ffb16c4e1a07c6dbfc968bd6649497c794a161cd"
strings:
$s1 = "passDs5Bu9Te7" fullword ascii
condition:
uint16(0) == 0x5a4d and $s1
}
This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Scenario: Scheduled System Backup Using DropBear SSH
Description: A legitimate scheduled backup job uses DropBear SSH to transfer backup files to a remote server.
Filter/Exclusion: process.name != "dropbear" OR process.parent.name != "crontab" OR process.parent.name != "systemd"
Scenario: Admin Task to Test SSH Connectivity
Description: An administrator manually tests SSH connectivity using DropBear to verify server availability.
Filter/Exclusion: process.user != "root" OR process.command_line NOT LIKE '%-p 22%'
Scenario: Remote Management via DropBear for Patching
Description: IT staff uses DropBear SSH to remotely apply system patches or updates to a server.
Filter/Exclusion: process.name != "dropbear" OR process.parent.name != "ssh" OR process.parent.name != "systemd"
Scenario: Internal Monitoring Tool Using DropBear SSH
Description: A monitoring tool like Nagios or Zabbix uses DropBear SSH to check server status or collect metrics.
Filter/Exclusion: process.name != "dropbear" OR process.parent.name != "nagios" OR process.parent.name != "zabbix"
Scenario: Legacy Application Using DropBear for Secure Communication
Description: A legacy internal application uses DropBear SSH to securely communicate with another internal service.
Filter/Exclusion: process.name != "dropbear" OR process.parent.name != "legacy_app" OR process.parent.name != "custom_service"