One of the biggest flaws exploited by Salt Typhoon hackers has had a patch available for years

• A security vulnerability in Microsoft Exchange servers remains largely unpatched
• A fix was issued four years ago, but some users clearly didn’t update
• This flaw may have aided the hacking group Salt Typhoon

Critical security vulnerabilities seem to be a regular occurrence in technology reporting, with countless patches and updates to keep track of – but this Microsoft Exchange Server flaw might be one to take very seriously.

Most of us will be familiar with the major incident in which 9 US telecom giants were breached in what appeared to be a Chinese state sponsored cyber-espionage campaign. The attack, attributed to hacking group Salt Typhoon, is said to have, at least in part, exploited a known critical security flaw in Microsoft Exchange Server.