Just quick PowerShell snippet to get list of created users in last 24 hours in your Active Directory.
$When = ((Get-Date).AddDays(-1)).Date Get-ADUser -Filter {whenCreated -ge $When} -Properties whenCreated
To get list of created groups in last 24 hours
$When = ((Get-Date).AddDays(-1)).Date Get-ADGroup -Filter {whenChanged -ge $When} -Properties whenChanged
Easily you can create nice report and send the output by email to keep record of changes.