An ongoing phishing campaign, active since at least April 2023, has been meticulously targeting Zimbra Collaboration email servers worldwide with the intention of stealing user credentials. The cybercriminals behind this operation have been deploying sophisticated phishing emails, impersonating Zimbra administrators, and falsely informing recipients of an imminent email server update that necessitates their attention.
Upon opening the attached HTML file, victims are directed to a convincingly crafted fake Zimbra login page, complete with company branding and a pre-filled username field, ultimately leading users to disclose their account passwords unwittingly.
The campaign, as outlined in a report by ESET, takes advantage of the apparent authenticity of the phishing page, successfully tricking individuals into submitting their credentials.
Additionally, some instances involve compromised administrator accounts to create new mailboxes, which are then exploited to disseminate phishing emails within organizations. Despite its relatively modest level of sophistication, the campaign’s widespread success underscores its impact, emphasizing the need for heightened vigilance among users of Zimbra Collaboration. This serves as a stark reminder that even seemingly minor vulnerabilities can be leveraged by threat actors to compromise critical systems and data.
The Zimbra email servers, long targeted by hackers, have become a favored entry point for cyber espionage and data breaches. Past incidents include the exploitation of vulnerabilities like CVE-2022-27926 by the Russian ‘Winter Vivern’ hacking group to access the webmail portals of high-profile organizations.
Similarly, the utilization of a zero-day flaw (CVE-2022-23682) by the ‘TEMP_Heretic’ threat actor illustrates the attractiveness of Zimbra Collaboration as a vector for lateral phishing attacks. ESET’s findings underscore the persistence of such threats, particularly as attackers continue to exploit widely-used platforms like Zimbra, especially within organizations with limited IT budgets.
