APT_HAFNIUM_ForensicArtefacts_WER_Mar21_1_RID3551

YARA detection rule by Florian Roth · CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/

Detects a Windows Error Report (WER) that indicates and exploitation attempt of the Exchange server as described in CVE-2021-26857 after the corresponding patches have been applied. WER files won't be written upon successful exploitation before applying the patch. Therefore, this indicates an unsuccessful attempt.

rule APT_HAFNIUM_ForensicArtefacts_WER_Mar21_1_RID3551 : APT CVE_2021_26857 DEMO FILE G0125 {
   meta:
      description = "Detects a Windows Error Report (WER) that indicates and exploitation attempt of the Exchange server as described in CVE-2021-26857 after the corresponding patches have been applied. WER files won't be written upon successful exploitation before applying the patch. Therefore, this indicates an unsuccessful attempt."
      author = "Florian Roth"
      reference = "https://twitter.com/cyb3rops/status/1368471533048446976"
      date = "2021-03-07 16:08:01"
      score = 50
      customer = "demo"
      license = "CC-BY-NC https://creativecommons.org/licenses/by-nc/4.0/"
      
      tags = "APT, CVE_2021_26857, DEMO, FILE, G0125"
      minimum_yara = "3.5.0"
      
   strings:
      $s1 = "AppPath=c:\\windows\\system32\\inetsrv\\w3wp.exe" wide fullword
      $s7 = ".Value=w3wp#MSExchangeECPAppPool" wide
   condition: 
      uint16 ( 0 ) == 0xfeff and filesize < 8KB and all of them
}

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

73ea0426-f6cf-407e-a954-7113acb2ea1f

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Executable code, not a declarative rule

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Rejected pattern present

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