Update whats-new.md

Brute force logic improvement aug25

Author: talgu4

ATPDocs/whats-new.md

@@ -23,6 +23,8 @@ For more information, see also:
 
 For updates about versions and features released six months ago or earlier, see the [What's new archive for Microsoft Defender for Identity](whats-new-archive.md).
 
+## August 2025
+**Suspected Brute Force attack (Kerberos, NTLM):** Improved detection logic now includes scenarios where accounts were locked during the attacks - note that the number of triggered alerts may increase.
 
 ## July 2025