Mass-spreading marketing campaign focusing on Zimbra customers

ESET Analysis

ESET researchers have noticed a brand new phishing marketing campaign focusing on customers of the Zimbra Collaboration electronic mail server.

17 Aug 2023
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5 min. learn

ESET researchers have uncovered a mass-spreading phishing marketing campaign, geared toward accumulating Zimbra account customers’ credentials, lively since not less than April 2023 and nonetheless ongoing. Zimbra Collaboration is an open-core collaborative software program platform, a well-liked various to enterprise electronic mail options. The marketing campaign is mass-spreading; its targets are a wide range of small and medium companies and governmental entities.

In keeping with ESET telemetry, the best variety of targets are positioned in Poland, adopted by Ecuador and Italy. Goal organizations differ: adversaries don’t give attention to any particular vertical with the one factor connecting victims being that they’re utilizing Zimbra. Thus far, we’ve got not attributed this marketing campaign to any recognized menace actors.

Initially, the goal receives an electronic mail with a phishing web page within the connected HTML file. As proven in Determine 2, Determine 3 and Determine 4, the e-mail warns the goal about an electronic mail server replace, account deactivation, or comparable challenge and directs the person to click on on the connected file. The adversary additionally spoofs the From: discipline of the e-mail to seem like an electronic mail server administrator.

Within the background, the submitted credentials are collected from the HTML kind and despatched by HTTPS POST request to a server managed by the adversary (Determine 7). The POST request vacation spot URLs use the next sample: https://<SERVER_ADDRESS>/wp-admin/ZimbraNew.php

Curiously, on a number of events we noticed subsequent waves of phishing emails despatched from Zimbra accounts of beforehand focused, respectable corporations, similar to donotreply[redacted]@[redacted].com. It’s probably that the attackers had been in a position to compromise the sufferer’s administrator accounts and created new mailboxes that had been then used to ship phishing emails to different targets. One clarification is that the adversary depends on password reuse by the administrator focused by phishing – i.e., utilizing the identical credentials for each electronic mail and administration. From obtainable knowledge we aren’t in a position to verify this speculation.

The marketing campaign noticed by ESET depends solely on social engineering and person interplay; nonetheless, this may increasingly not all the time be the case. In a earlier marketing campaign described by Proofpoint in March 2023, the APT group Winter Vivern (aka TA473) had been exploiting the CVE-2022-27926 vulnerability, focusing on webmail portals of army, authorities, and diplomatic entities of European international locations. In one other instance, reported by Volexity in February 2022, a bunch named TEMP_Heretic exfiltrated emails of European authorities and media organizations by abusing one other vulnerability (CVE-2022-24682) within the Calendar characteristic in Zimbra Collaboration. In the latest point out, EclecticIQ researchers analyzed a marketing campaign much like the one described in our blogpost. The primary distinction is that the HTML hyperlink resulting in the faux Zimbra login web page is positioned instantly within the electronic mail physique.

Conclusion

Regardless of this marketing campaign not being so technically refined, it’s nonetheless in a position to unfold and efficiently compromise organizations that use Zimbra Collaboration, which stays a horny goal for adversaries. Adversaries leverage the truth that HTML attachments comprise respectable code, and the one telltale aspect is a hyperlink pointing to the malicious host. This manner, it’s a lot simpler to bypass reputation-based antispam insurance policies, in comparison with phishing strategies the place a malicious hyperlink is instantly positioned within the electronic mail physique. The recognition of Zimbra Collaboration amongst organizations anticipated to have decrease IT budgets ensures that it stays a horny goal for adversaries.

For any inquiries about our analysis revealed on WeLiveSecurity, please contact us at threatintel@eset.com.
ESET Analysis presents personal APT intelligence experiences and knowledge feeds. For any inquiries about this service, go to the ESET Risk Intelligence web page.

IOCs

ESET detection names

HTML/Phishing.Gen

Information

We’re unable to share file IoCs as a result of samples comprise delicate info.

Community

Hosts used to exfiltrate harvested credentials are hosted on shared servers. Detections based mostly solely on IP addresses might result in false positives.

URLs

https://fmaildd.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://mtatdd.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://nmailddt.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://posderd.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://ridddtd.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://tmaxd.000webhostapp[.]com/wp-admin/ZimbraNew.php
https://zimbra.y2kportfolio[.]com/wp/wp-admin/ZimbraNew.php

MITRE ATT&CK

This desk was constructed utilizing model 13 of the MITRE ATT&CK framework.