Event 4755: A security-enabled universal group was changed.

Adversaries may manipulate accounts to maintain and/or elevate access to victim systems. Account manipulation may consist of any action that preserves or modifies adversary access to a compromised account, such as modifying credentials or permission groups.(Citation: FireEye SMOKEDHAM June 2021) These actions could also include account activity designed to subvert security policies, such as performing iterative password updates to bypass password duration policies and preserve the life of compromised credentials. In order to create or manipulate accounts, the adversary must already have sufficient permissions on systems or the domain. However, account manipulation may also lead to privilege escalation where modifications grant access to additional roles, permissions, or higher-privileged [Valid Accounts](https://attack.mitre.org/techniques/T1078).

An adversary may add additional local or domain groups to an adversary-controlled account to maintain persistent access to a system or domain. On Windows, accounts may use the `net localgroup` and `net group` commands to add existing users to local and domain groups.(Citation: Microsoft Net Localgroup)(Citation: Microsoft Net Group) On Linux, adversaries may use the `usermod` command for the same purpose.(Citation: Linux Usermod) For example, accounts may be added to the local administrators group on Windows devices to maintain elevated privileges. They may also be added to the Remote Desktop Users group, which allows them to leverage [Remote Desktop Protocol](https://attack.mitre.org/techniques/T1021/001) to log into the endpoints in the future.(Citation: Microsoft RDP Logons) On Linux, accounts may be added to the sudoers group, allowing them to persistently leverage [Sudo and Sudo Caching](https://attack.mitre.org/techniques/T1548/003) for elevated privileges. In Windows environments, machine accounts may also be added to domain groups. This allows the local SYSTEM account to gain privileges on the domain.(Citation: RootDSE AD Detection 2022)