Saturday, March 2, 2024

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 e mail server.

Mass-spreading campaign targeting Zimbra users

ESET researchers have uncovered a mass-spreading phishing marketing campaign, geared toward accumulating Zimbra account customers’ credentials, energetic since not less than 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 line with ESET telemetry, the best variety of targets are positioned in Poland, adopted by Ecuador and Italy. Goal organizations fluctuate: adversaries don’t give attention to any particular vertical with the one factor connecting victims being that they’re utilizing Zimbra. Up to now, we have now not attributed this marketing campaign to any recognized risk actors.

Countried hit by the campaign

Determine 1. Nations hit by the marketing campaign, in keeping with ESET telemetry

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 related situation and directs the consumer to click on on the connected file. The adversary additionally spoofs the From: subject of the e-mail to look like an e mail server administrator.

Zimbra warning

Determine 2. Lure e mail warning in Polish about deactivation of the goal’s Zimbra account

Translated lure email

Determine 3. Machine translation of lure e mail, initially in Polish

Lure email in italian

Determine 4. Lure e mail in Italian; that means is similar as in Determine 3

After opening the attachment, the consumer is offered with a pretend Zimbra login web page personalized in keeping with the focused group, as proven in Determine 5. The HTML file is opened within the sufferer’s browser, which could trick the sufferer into believing they have been directed to the official login web page, regardless that the URL factors to an area file path. Notice that the Username subject is prefilled within the login type, which makes it seem extra official.

Fake login

Determine 5. Pretend Zimbra login web page

In Determine 6 we’re offering an instance of official Zimbra webmail login web page for the comparability. 

Legitimate login

Determine 6. Instance of a official Zimbra login web page

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

Code snippet

Determine 7. Code snippet liable for the POST request exfiltrating targets’ credentials

Curiously, 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 capable of 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 way of phishing – i.e., utilizing the identical credentials for each e mail and administration. From accessible information we’re not capable of verify this speculation.

The marketing campaign noticed by ESET depends solely on social engineering and consumer interplay; nonetheless, this will not at all times 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 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 function in Zimbra Collaboration. In the latest point out, EclecticIQ researchers analyzed a marketing campaign much like the one described in our blogpost. The principle distinction is that the HTML hyperlink resulting in the pretend Zimbra login web page is positioned instantly within the e mail physique.


Regardless of this marketing campaign not being so technically subtle, it’s nonetheless capable of unfold and efficiently compromise organizations that use Zimbra Collaboration, which stays a lovely goal for adversaries. Adversaries leverage the truth that HTML attachments include official code, and the one telltale factor is a hyperlink pointing to the malicious host. This manner, it’s a lot simpler to avoid 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
ESET Analysis provides personal APT intelligence studies and information feeds. For any inquiries about this service, go to the ESET Risk Intelligence web page.


ESET detection names



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


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



Internet hosting supplier

First seen




Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Hostinger Worldwide Ltd, NL


Malicious host used to exfiltrate harvested credentials.



Eonix Company, US


Malicious host used to exfiltrate harvested credentials.




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





Useful resource Growth


Compromise Accounts: E mail Accounts

The adversary used beforehand compromised e mail accounts for marketing campaign spreading.


Set up Accounts: E mail Accounts

The adversary created new e mail accounts to facilitate the marketing campaign. 

Preliminary Entry


Phishing: Spearphishing Attachment

The marketing campaign was unfold by malicious HTML recordsdata in e mail attachments.



Consumer Execution: Malicious File

A profitable assault depends on the sufferer clicking on a malicious file within the attachment.



Create Account

The adversary created new e mail accounts on compromised Zimbra situations for additional spreading of the phishing marketing campaign.



Enter Seize: Internet Portal Seize

The adversary captured credentials inserted to a pretend login web page.



Exfiltration Over Different Protocol: Exfiltration Over Uneven Encrypted Non-C2 Protocol

The adversary exfiltrated passwords by POST requests despatched over the HTTPS protocol.

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