Office 365 Shell Attack

Protecting Your Office 365 Account from Access Token/Shell Attacks

Let’s examine a crucial security issue many Office 365 users face: the Access Token Attack, also known as a Shell Attack. If you use Office 365 (O365), understanding this topic is essential for safeguarding your account.

What is an Access Token Attack?

An access token attack is a technique hackers increasingly use to gain unauthorized access to your Office 365 account. When you log into Office 365, you've likely noticed a checkbox that says, "Stay logged in. " This checkbox generates a token allowing you to remain signed in without re-entering your credentials each time. Hackers exploit this feature by stealing that token through phishing, spear phishing, or malware.

Once they have your token, hackers gain the same access and permissions as you do. This means they can log into your Office 365 account, view and send emails, and potentially cause substantial damage within your organization.

How to Protect Against Access Token Attacks

Here are several best practices to protect yourself from this kind of threat:

1. Avoid the “Stay Logged In” Option
   When prompted to "Stay logged in," consider saying “No.” While it might be less convenient, not using this option will reduce the risk of access token misuse. Staying logged in might save you a few seconds, but it opens the door to severe vulnerabilities.
2. Deny Existing Access Tokens
   If you suspect unauthorized access or a token may have been compromised, setting up rules to deny existing access tokens and require new ones to be generated is essential. This action will prevent an attacker from using an old token to access your account.
3. Implement a Cloud Access Security Broker (CASB)
   Adding a CASB to your security setup provides an extra layer of protection by allowing access to your Office 365 account only through specific, trusted IP addresses. This restriction means that hackers must compromise the CASB to access your account, which adds a significant barrier.
4. Use Conditional Access Policies with Azure AD Premium P2
   For those with an Azure Active Directory Premium P2 license, "Conditional Access" policies enable highly customizable access controls for Office 365. Conditional Access allows you to limit access based on the user’s location, device, and other criteria, making it harder for unauthorized access.

Need Help Securing Your Office 365?

At ADS Consulting Group, we specialize in security solutions for businesses and organizations. If you’d like assistance preventing access token attacks or implementing a CASB for Office 365, feel free to email us info@adscon.com.