Cyber Security Threat Summary:
FortiEDR research lab has identified a targeted attack against a government entity in the United Arab Emirates, involving a custom PowerShell-based backdoor called PowerExchange. The backdoor utilizes the victim's Microsoft Exchange server as its command and control (C2) server, operating through an email-based C2 protocol. The investigation revealed multiple implants and a unique web shell named ExchangeLeech, capable of credential harvesting. The indicators point to an Iranian threat actor as the perpetrator of these attacks. The attack chain starts with email phishing and the execution of a malicious .NET executable. The backdoor establishes communication with the Exchange server, sends and receives commands through mailboxes, and executes malicious payloads.

Security Officer Comments:
The PowerExchange backdoor demonstrates a sophisticated attack technique that leverages the victim's own Exchange server for C2 communication, enabling the threat actor to evade network-based detections. The use of web shells and implant variations further highlights the attacker's capabilities and persistence. Endpoint security solutions are crucial for comprehensive protection, and organizations must be vigilant in educating users about phishing threats, which remain an effective method for initial compromise.

Suggested Correction(s):
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.

Link(s):
https://www.fortinet.com/blog/threat-research/operation-total-exchange-backdoor-discovered