The hypothesis is that the detection rule identifies potential adversary activity involving the execution of a suspicious file with a unique identifier, which may indicate a novel or custom malware payload. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential advanced persistent threat (APT) activities that may evade traditional detection methods.
YARA Rule
rule sig_7acb8d6d4c062c3097a7d31df103bc4d018519f9 {
meta:
description = "Auto-generated rule - file 7acb8d6d4c062c3097a7d31df103bc4d018519f9.codex"
author = "YarGen Rule Generator"
reference = "not set"
date = "2016-07-21"
hash1 = "e1607486cbb2d111d5df314fe58948aa0dc5897f56f7fd763c62bb30651380e3"
strings:
$s1 = "5(666Z6c6" fullword ascii
$s2 = "Wlm;y%UD%d" fullword ascii
$s3 = ";1;9;@;G;N;U;\\;c;j;q;x;" fullword ascii
$s4 = "8 8'8.858<8C8J8Q8X8_8f8m8t8" fullword ascii
$s5 = "2 2,282=2B2G2P2U2Z2_2h2s2x2" fullword ascii
$s6 = "4'5.555<5C5J5Q5X5_5f5m5t5{5" fullword ascii
$s7 = "0#0*01080?0F0M0T0[0b0i0p0w0" fullword ascii
$s8 = "6$6,616=6B6G6S6X6]6i6n6s6" fullword ascii
$s9 = "=\"=)=0=7=>=E=L=S=Z=a=h=" fullword ascii
$s10 = "6&6-646;6B6I6P6W6^6e6l6s6z6" fullword ascii
$s11 = "O.QrH@" fullword ascii
$s12 = ">\">/>4>A>F>S>X>e>j>w>|>" fullword ascii
$s13 = "0#0(040=0B0N0T0Y0e0k0p0|0" fullword ascii
$s14 = "5)5/545@5F5K5W5`5e5q5w5|5" fullword ascii
$s15 = "=!=&=3=8=E=N=S=`=e=s=x=}=" fullword ascii
$s16 = ":(:/:6:=:D:K:R:Y:`:g:n:u:|:" fullword ascii
$s17 = "7\"727<7F7M7W7a7k7u7" fullword ascii
$s18 = "2+21262E2K2P2\\2h2m2|2" fullword ascii
$s19 = ";/;5;:;G;V;\\;a;n;};" fullword ascii
$s20 = ";\";-;8;C;N;^;i;t;" fullword ascii
$op0 = { ff 44 24 14 8d 47 44 50 a1 08 63 44 00 ff 90 84 } /* Opcode */
$op1 = { 6d 43 00 c7 84 24 10 03 00 00 0c 6d 43 00 c7 84 } /* Opcode */
$op2 = { c7 43 0c 20 02 00 00 89 5d f0 ff 90 f8 } /* Opcode */
condition:
( uint16(0) == 0x5a4d and filesize < 900KB and ( 10 of ($s*) )and 1 of ($op*) ) or ( all of them )
}This YARA rule can be deployed in the following contexts:
This rule contains 23 string patterns in its detection logic.
Scenario: A system administrator is using PowerShell to automate the deployment of a new application, which involves executing a script with a filename matching the rule’s signature.
Filter/Exclusion: process.name != "powershell.exe" OR process.parent.name == "task scheduler" OR process.args contains "deploy"
Scenario: A scheduled task (via Task Scheduler) is running a legitimate maintenance script that temporarily creates a file with the same name as the rule’s signature.
Filter/Exclusion: process.parent.name == "task scheduler" OR process.parent.process_id == <task_scheduler_process_id>
Scenario: A backup tool like Veeam or Commvault is generating temporary files during a backup operation, which matches the rule’s file signature.
Filter/Exclusion: process.name contains "veeam" OR process.name contains "commvault" OR process.args contains "backup"
Scenario: An IT admin is using Windows Server Manager to perform a system update, which creates temporary files with the same name as the rule’s signature.
Filter/Exclusion: process.name contains "servermanager" OR process.parent.name == "services.exe" OR process.args contains "update"
Scenario: A configuration management tool like Ansible or Chef is executing a playbook that generates a file with the same name as the rule’s signature during a configuration push.
Filter/Exclusion: process.name contains "ansible" OR process.name contains "chef" OR process.args contains "playbook"