As an avid Outlook user myself, I was alarmed to learn of a serious vulnerability recently uncovered by the skilled cybersecurity researchers at Varonis. In July 2023, they detected a loophole in Outlook’s calendar system that could allow hackers to access users’ password information.
Microsoft responded quickly by releasing a security patch on December 12th, just 5 months later. However, any Outlook users who have not yet updated are still vulnerable.
I urge you to implement the latest patch immediately to lock the hackers out!
Understanding the Calendar Invite Risk
This security flaw allows potential hackers to embed malicious code inside Outlook’s calendar invite files. If you click to accept one of these infected invites, the harmful code will execute remotely on your device.
It’s designed to steal your password information in the form of NTLM hashes. With these hashes in hand, the hackers can use brute force methods to crack your actual passwords.
Even worse, they can capture your current login session using relay attacks and access your account directly, no cracking required! Just one simple click on a calendar invite unleashes these risks.
Defending Your Data Against the Outlook Flaw
- The best technical protections involve upgrading Outlook’s outdated NTLM authentication. By transitioning to the more secure Kerberos authentication standard, most password-stealing attacks are blocked.
- You should also configure your Outlook settings to disable NTLM version 2, as this is the specific protocol targeted in this attack.
- Finally, use a reputable SMB security solution to monitor for man-in-the-middle attacks against your server messaging blocks (SMBs). Adopting measures like these will keep the hackers at bay.
Simple Practices to Safeguard Your Account
- As mentioned already, installing Microsoft’s security updates is critical – always accept the latest patches to stay ahead of emerging threats.
- Additionally, I advise all Outlook users to carefully inspect calendar invites before accepting them. Check that the sender’s name, email address and domains match expectations. Does the event seem relevant based on recent correspondence? If anything seems suspicious, it’s safest to ignore the invite altogether.
- Staying alert protects you and your data.
In closing, I hope this outline of Outlook’s current vulnerability and recommended safeguards assists you in locking down your account.
Though alarming at first glance, adopting both technical and common-sense security practices will keep you well protected.
Reach out anytime if you need help bolstering your cyber defenses!
