Mass-spreading marketing campaign concentrating on Zimbra customers

ESET Analysis

ESET researchers have noticed a brand new phishing marketing campaign concentrating on customers of the Zimbra Collaboration e 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, energetic since no less than April 2023 and nonetheless ongoing. Zimbra Collaboration is an open-core collaborative software program platform, a well-liked different to enterprise e 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 situated in Poland, adopted by Ecuador and Italy. Goal organizations differ: adversaries don’t deal with any particular vertical with the one factor connecting victims being that they’re utilizing Zimbra. Up to now, we’ve not attributed this marketing campaign to any identified menace actors.

Initially, the goal receives an e 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 e mail server replace, account deactivation, or comparable concern and directs the person to click on on the connected file. The adversary additionally spoofs the From: discipline of the e-mail to look like an e mail server administrator.

Within the background, the submitted credentials are collected from the HTML type 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

Apparently, on a number of events we noticed subsequent waves of phishing emails despatched from Zimbra accounts of beforehand focused, official firms, resembling donotreply[redacted]@[redacted].com. It’s seemingly that the attackers have been in a position to compromise the sufferer’s administrator accounts and created new mailboxes that have 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 means of phishing – i.e., utilizing the identical credentials for each e mail and administration. From accessible information we’re not in a position to verify this speculation.

The marketing campaign noticed by ESET depends solely on social engineering and person interplay; nevertheless, 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, concentrating on webmail portals of navy, authorities, and diplomatic entities of European international locations. In one other instance, reported by Volexity in February 2022, a gaggle named TEMP_Heretic exfiltrated emails of European authorities and media organizations by abusing one other vulnerability (CVE-2022-24682) within the Calendar function in Zimbra Collaboration. In the newest point out, EclecticIQ researchers analyzed a marketing campaign just like the one described in our blogpost. The primary distinction is that the HTML hyperlink resulting in the faux Zimbra login web page is situated instantly within the e mail physique.

Conclusion

Regardless of this marketing campaign not being so technically subtle, it’s nonetheless in a position to unfold and efficiently compromise organizations that use Zimbra Collaboration, which stays a lovely goal for adversaries. Adversaries leverage the truth that HTML attachments comprise official code, and the one telltale ingredient 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 e mail physique. The recognition of Zimbra Collaboration amongst organizations anticipated to have decrease IT budgets ensures that it stays a lovely goal for adversaries.

For any inquiries about our analysis revealed on WeLiveSecurity, please contact us at threatintel@eset.com.
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IOCs

ESET detection names

HTML/Phishing.Gen

Information

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

Community

Hosts used to exfiltrate harvested credentials are hosted on shared servers. Detections based mostly solely on IP addresses may 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.