Tag: Incident Response

Defense

Post Business Email Compromise actions for Office 365 Users

If you have a business email compromise incident and you haven’t deteced it in a timely manner your fist notification might be a bad experiance, the threat actors may have commited fraud, attemped fraud or simply launched a phishing If you have a business email compromise incident and you haven’t detected it in a timely manner your fist notification might be a bad experience, the threat actors may have committed fraud, attempted fraud, or simply launched a phishing campaign from your environment. If you are in this position, there are some steps you can take from a technical point of view to limit impact and reduce risk of a re-occurrence. This blog is a high-level view at some of the tactical and longer-term activities you can conduct.

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Defense

Post Compromise Active Directory Checklist

Nuke it from orbit, it’s the only way to be sure!

Ok, in an ideal world you can re-deploy your entire environment from scratch, but back in the most people’s real world’s that’s not that simple. So, what do we do if we can’t nuke from orbit in a post compromise situation? Well, we need to clean up! This isn’t an exhaustive list, not a total guide. it’s a quick list to make you think about some key common areas and actions that might need to be taken! after all if someone got r00t, who knows what they did! (trust me, most orgs monitoring is a bit naff!)

Potential Actions

  • Reset all user account passwords twice (thanks @tazwake)
    • Reset all administrator passwords
    • Reset all service accounts passwords
  • Reset (twice – but bear in mind the issues with replication so there’s specific guidance on this) the KRBTGT password
  • Reset all computer account passwords
  • Check the value of the computer account password change value
  • Reset all LAPS Passwords
  • Reset permissions on AdminSDHolders object
  • Revoke and re-issue all certificates from ADCS
  • Check for malicious scheduled tasks (thanks @SchizoDuckie)
  • Check for malicious WMI event filters
  • Check for malicious autoruns or other registry-based persistence mechanisms
  • Check for utilman style backdoors
  • Check for malicious printers/printer drivers (thanks @SchizoDuckie)
  • Review Active Directory Delegated access permissions (thank https://twitter.com/@indachtig)
  • Rotate ADFS token signing and token decryption certificates (thanks @4n6Bexaminer)
  • Check Service Control Manager (SCM) security descriptors (https://docs.microsoft.com/en-us/windows/win32/services/service-security-and-access-rights) (thanks @EricaZeli)
  • Check for object changes around initial access/event timescales (thanks @IISResetMe)
  • Validate group memberships against known baselines (replication metadata, backup, AD reporting tools/reports etc.) (thanks @IISResetMe)
  • Harden Active Directory (look at pingcastle and MITRE) (thanks @MarkSewe)
  • Review logon scripts in GPOS and SYSVOL (thanks @CisoDiagonal and A-HAX!)
  • Rotate Group Managed Service Accounts (GMSA) (thanks @infosecspy)
  • Rotate LAPS credentials
  • Review Azure AD/AD Connect (thanks @infosecspy)
  • Harden Endpoints
  • Update AV
  • Deploy EDR
  • Deploy SYSMON
  • DNS Zone Integrity (Public and Private) (thanks to @jermuv)
  • Rote domain trust keys (thanks @DebugPrivilege)
  • Review potential RBCD Bakdoors (thanks @DebugPrivilege)
  • Review msDsConsistencyGuid attribute of compromised accounts (thanks @DebugPrivilege)
  • Check Exchange (easy right?)
  • Review accounts for “Key Trust Account Mapping” takeover and reset if required (thanks @nodauf)
    • https://posts.specterops.io/shadow-credentials-abusing-key-trust-account-mapping-for-takeover-8ee1a53566ab
  • Review Active Directory Domains and Trusts (thanks @dragon199421)
  • Deploy new Domain Controllers (keep existing forest/domain metadata)
  • Clear VSS/Backups/Snapshots that are likely to be classed as unsafe (thanks to @Digit4lbytes) Read more “Post Compromise Active Directory Checklist” →