eScan antivirus users were infected with malware last week after hackers compromised an official update server, security researchers report.
The eScan supply chain attack came to light on January 29, when cybersecurity firm Morphisec published a threat bulletin warning of rogue updates tampering with users’ systems.
“Malicious updates were distributed through eScan’s legitimate update infrastructure, resulting in the deployment of multi-stage malware to enterprise and consumer endpoints globally,” Morphisec’s bulletin reads.
According to the security firm, the updates modified users’ devices so that they would be cut off from eScan’s updates. The antivirus’s normal functionality was also altered, it says.
The affected users received a malicious ‘Reload.exe’ file, designed to kick off a multi-stage infection chain. The file modified the HOSTS file to block automatic updates, established persistence through scheduled tasks, and downloaded additional payloads.
“Automatic remediation is therefore not possible for compromised systems. Impacted organizations and individuals must proactively contact eScan to obtain the manual update/patch,” Morphisec says.
Morphisec said it reported the incident to MicroWorld Technologies, the company behind eScan, on January 21, one day after it detected the malicious behavior on its customers’ devices.
eScan informed Morphisec that it had detected unauthorized access to its infrastructure on January 20 and immediately isolated the impacted update servers, which remained offline for over eight hours.
To resolve the issue, eScan released a utility that users can obtain by contacting the company’s technical support team. The tool was designed to clean the infection, roll back malicious system modifications, and restore eScan’s normal functionality.
eScan downplays impact, cries foul play
While the attack and the aftermath seem rather straightforward, eScan’s reaction to the public disclosure of the incident is a different story.
As it turns out, the Indian antivirus provider was not happy with Morphisec’s assessment of how the incident unfolded, nor with the “supply chain attack” stamp slapped on it.
The company, however, did confirm the unauthorized access to its infrastructure. In fact, it disclosed it to its customers in a January 22 security advisory, which states that the incident impacted a regional update server.
“Unauthorized access to one of our regional update server configurations resulted in an incorrect file (patch configuration binary/corrupt update) being placed in the update distribution path. This file was distributed to customers downloading updates from the affected server cluster during a limited timeframe on January 20, 2026,” the advisory reads.
The advisory’s description of the system behavior triggered by the malicious update overlaps with Morphisec’s description. Additionally, eScan notes that the incident had a medium-high impact on enterprise customers, which fits Morphisec’s assessment.
Regardless, eScan is unhappy with Morphisec’s reporting on the incident, which it sees as inaccurate, noting that it found no evidence of additional malware being downloaded. In fact, the antivirus company told SecurityWeek it was working with legal counsel on the matter.
eScan says it has fully resolved the incident, has remediated all impacted customers, and that it has no evidence of additional malicious downloads, of data exfiltration, or remote access capabilities being deployed.
“Due to the limited timeframe (approximately 2 hours) and specific geographic/infrastructure scope, the impact was contained to a small subset of our customer base. For customer privacy and security reasons, we do not disclose specific customer counts,” eScan said.
The antivirus company underlined that it detected the incident before any external notification, that it took its global update infrastructure offline to address the issue, performed forensic analysis, built and tested remediation tools, and rebuilt the affected infrastructure with enhanced security.
“eScan takes security incidents seriously and responds swiftly. We detected this incident through our own monitoring, immediately issued customer advisories and patches, and contained the situation within days. We provided comprehensive support to all affected customers and implemented enhanced security measures to prevent recurrence. We are concerned that some third-party reports contain multiple demonstrably false technical claims that we have documented in detail. We stand behind the accuracy of our incident response and the integrity of our products,“ eScan said.
*Updated with statement from eScan.
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