Action Copied and Removed Web Shells that Provided Backdoor Access to Servers, but Additional Steps may be Required to Patch Exchange Server Software and to Expel Hackers from the Victims’ Networks.
WASHINGTON – The Justice Department has initiated a court-authorized operation to copy and remove malicious web shells from hundreds of vulnerable computers in the United States running on-premises versions of Microsoft Exchange Server software used to provide enterprise-level e-mail service.
Through January and February 2021, certain hacking groups exploited zero-day vulnerabilities in Microsoft Exchange Server software to access e-mail accounts and place web shells (which are pieces of code or scripts that enable remote administration) for continued access. Other hacking groups followed suit starting in early March after the vulnerability and patch were publicized. Although many infected system owners successfully removed the web shells from thousands of computers, others appeared unable to do so, and hundreds of such web shells persisted unmitigated.