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 amassing Zimbra account customers’ credentials, energetic since at the very least April 2023 and nonetheless ongoing. Zimbra Collaboration is an open-core collaborative software program platform, a preferred 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 response to ESET telemetry, the best variety of targets are situated in Poland, adopted by Ecuador and Italy. Goal organizations differ: adversaries don’t concentrate on any particular vertical with the one factor connecting victims being that they’re utilizing Zimbra. To this point, now we have not attributed this marketing campaign to any recognized menace actors.

Initially, the goal receives an e mail with a phishing web page within the hooked up 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 related subject and directs the consumer to click on on the hooked up file. The adversary additionally spoofs the From: subject of the e-mail to look like an e 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

Apparently, on a number of events we noticed subsequent waves of phishing emails despatched from Zimbra accounts of beforehand focused, respectable corporations, resembling donotreply[redacted]@[redacted].com. It’s doubtless 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 via phishing – i.e., utilizing the identical credentials for each e mail and administration. From accessible knowledge we aren’t in a position to verify this speculation.

The marketing campaign noticed by ESET depends solely on social engineering and consumer 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 nations. 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 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 pretend Zimbra login web page is situated straight 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 include respectable code, and the one telltale component is a hyperlink pointing to the malicious host. This fashion, it’s a lot simpler to avoid reputation-based antispam insurance policies, in comparison with phishing strategies the place a malicious hyperlink is straight 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 [email protected].
ESET Analysis gives personal APT intelligence studies and knowledge feeds. For any inquiries about this service, go to the ESET Menace Intelligence web page.

IOCs

ESET detection names

HTML/Phishing.Gen

Information

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

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.