Cyber Security Threat Summary:
Microsoft researchers have issued a warning about a new form of cyber attack known as "adversary-in-the-middle" (AiTM) phishing and business email compromise (BEC), specifically targeting banking and financial institutions. These attacks involve threat actors creating a proxy server that sits between a user and their desired website. The proxy server, controlled by the attackers, intercepts and captures the user's password and session cookie, allowing the attackers to gain unauthorized access to sensitive information.

“Microsoft discovered that the attackers initially compromised a trusted vendor, then targeted multiple organizations with AiTM attacks and follow-on BEC activities. “This attack shows the complexity of AiTM and BEC threats, which abuse trusted relationships between vendors, suppliers, and other partner organizations with the intent of financial fraud.” reads the analysis published by Microsoft. “While the attack achieved the end goal of a typical AiTM phishing attack followed by business email compromise, notable aspects, such as the use of indirect proxy rather than the typical reverse proxy techniques, exemplify the continuous evolution of these threats.” This campaign outstands for the use of an indirect proxy that provided attackers control and flexibility in tailoring the phishing pages to their targets and steal session cookies. Upon signing in with the stolen cookie through a session replay attack, the attackers leveraged multifactor authentication (MFA) policies that have not properly to update MFA methods without an MFA challenge. Then the attacker sent out more than 16,000 emails to the target’s contacts as part of a second-stage phishing campaign. Microsoft states that affected organizations need to revoke session cookies and roll back modifications made by the threat actor in the MFA process” (SecurityAffairs, 2023).

Security Officer Comments:
The attack is attributed to Storm-1167, as the emerging cluster responsible for these malicious activities. The attack chain commences with a phishing email containing a deceptive link leading to a counterfeit Microsoft sign-in page. This page aims to deceive recipients into divulging their login credentials and 2FA code. Subsequently, the attackers employ the stolen credentials and session cookies to gain unauthorized access to the victim's email inbox via a replay attack. The compromised data is then utilized to execute a business email compromise (BEC) attack. Further, Microsoft noted the connection between the AiTM phishing attack and second-stage BEC.

Suggested Correction(s):


General Phishing Mitigations:
Users should always be cautious of individuals or organizations that ask for personal information. Most companies will not ask for sensitive data from its customers. If in doubt, users should verify with the company itself to avoid any potential issues.

Users should always take a close look at the sender’s display name when checking the legitimacy of an email. Most companies use a single domain for their URLs and emails, so a message that originates from a different domain is a red flag.

As a general rule, users should not click links or download files even if they come from seemingly “trustworthy” sources.

Check for mismatched URLs. While an embedded URL might seem perfectly valid, hovering above it might show a different web address. In fact, users should avoid clicking links in emails unless they are certain that it is a legitimate link.

Users should always be on the lookout for any grammatical errors and spelling mistakes. Legitimate companies will often employ proofreaders and editors who ensure that the materials they send out are error-free.

Users should not be frightened or intimidated by messages that have an alarmist tone. They should double check with the company if they are uncertain about the status of their accounts.

Phishing emails are designed to be sent to a large number of people, so they need to be as impersonal as possible. Users should check whether the message contains a generic subject and greeting, as this can be a sign of a phishing attempt.

Although not every end user has access to advanced anti-phishing software, they can still use the built-in protection of their email clients to filter messages. One example is setting the email client to block all images unless approved.

Legitimate companies will never send confirmation emails unless there are specific reasons for doing so. In fact, most companies will avoid sending unsolicited messages unless it’s for company updates, newsletters, or advertising purposes.

Users should always take the context of an email or message into account. For example, most online accounts do away with viewable member numbers, so users should be wary if they receive emails containing a “member number” for services that generally don’t use them.

It is important to take note of unusual information in the text of the message. Any mentions of operating systems and software that are not typically used by consumers can often be indicators of a phishing attempt.

If it seems suspicious, it probably is. Users should always err on the side of caution when it comes to sending out personally identifiable information through messages and emails.

BEC Mitigations: BEC attacks are harder to defend against than traditional phishing because common indicators like bad domains are not used. Because communications are coming from trusted and expected partners, employees will be more likely to fall victim to attacks.

The only real prevention is to train employees to spot BEC attacks. Employees should understand that every email received could be malicious. If you receive a strange invoice, wire transfer request, or unexpected email from a trusted user, verification via phone is recommended. Never use email communications to verify a payment request, because the account may still be compromised by the threat actor.

Avoid requests that prey on emotions, have a sense of urgency, or just feel off. While emails may be coming from a trusted sender, spelling mistakes and bad grammar seen in normal phishing emails may still be present.

To avoid falling victim to BEC yourself, multifactor authentication is recommended on all email accounts. Users should monitor leak websites and leverage security tools that monitor for stolen or leaked credentials.

Link(s):
https://securityaffairs.com/147327/hacking/aitm-bec-attacks.html