New Conversation Hijacking Campaign Delivering IcedID

In the new IcedID campaign Intezer has discovered is a further evolution of the threat actors' technique. The threat actor now uses compromised Microsoft Exchange servers to send the phishing emails from the account that they stole from.

The payload has also moved away from using office documents to the use of ISO files with a Windows LNK file and a DLL file. The use of ISO files allows the threat actor to bypass the Mark-of-the-Web controls, resulting in execution of the malware without warning to the user.

With regards to targeting, we have seen organizations within energy, healthcare, law, and pharmaceutical sectors.

Key Characteristics of the IcedID Phishing Campaign

• The attack-chain starts with a phishing email.
• The email includes a message about some important document and has a password protected "zip" archive file attached.
• The password to the archive is given in the email body.
• What makes the phishing email more convincing is that it's using conversation hijacking (thread hijacking).
• A forged reply to a previous stolen email is being used.
• Additionally, the email has also been sent from the email account from whom the email was stolen from.

Summary

This latest IcedID campaign demonstrates a growing sophistication in phishing operations. By hijacking real email threads and sending messages from compromised accounts, attackers significantly improve their chances of bypassing defenses and deceiving recipients. The shift to ISO-based payloads further enhances their ability to evade detection and deliver malware without user warnings.