Adversaries may interrupt availability of system and network resources by inhibiting access to accounts utilized by legitimate users. Accounts may be deleted, locked, or manipulated (ex: changed credentials, revoked permissions for SaaS platforms such as Sharepoint) to remove access to accounts.(Citation: Obsidian Security SaaS Ransomware June 2023) Adversaries may also subsequently log off and/or perform a System Shutdown/Reboot to set malicious changes into place.(Citation: CarbonBlack LockerGoga 2019)(Citation: Unit42 LockerGoga 2019) In Windows, Net utility, <code>Set-LocalUser</code> and <code>Set-ADAccountPassword</code> PowerShell cmdlets may be used by adversaries to modify user accounts. Accounts could also be disabled by Group Policy. In Linux, the <code>passwd</code> utility may be used to change passwords. On ESXi servers, accounts can be removed or modified via esxcli (`system account set`, `system account remove`). Adversaries who use ransomware or similar attacks may first perform this and other Impact behaviors, such as Data Destruction and Defacement, in order to impede incident response/recovery before completing the Data Encrypted for Impact objective.
Invocation of esxcli 'system account remove' from vCLI, SSH, or vSphere API with anomalous user access or outside maintenance windows.
Correlated user account modification (reset, disable, deletion) events with anomalous process lineage (e.g., PowerShell or net.exe from an interactive session), especially outside of IT admin change windows or by non-admin users.
Password changes or account deletions via 'passwd', 'userdel', or 'chage' preceded by interactive shell or remote command execution from non-privileged accounts.