Security researchers from antivirus vendor Trend Micro have uncovered a piece of backdoor-type malware that infects Java-based HTTP servers and allows attackers to execute malicious commands on the underlying systems.
The threat, known as BKDR_JAVAWAR.JG, comes in the form of a JavaServer Page (JSP), a type of Web page that can only be deployed and served from a specialised Web server with a Java servlet container, such as Apache Tomcat.
Once this page is deployed, the attacker can access it remotely and can use its functions to browse, upload, edit, delete, download or copy files from the infected system using a Web console interface. This is similar to the functionality provided by PHP-based backdoors, commonly known as PHP Web shells.
"Aside from gaining access to sensitive information, an attacker gains control of the infected system thru the backdoor and can carry out more malicious commands onto the vulnerable server," Trend Micro researchers said Thursday in a blog post.
This JSP backdoor can be installed by other malware already running on the system that hosts the Java-based HTTP server and Java servlet container or can be downloaded when browsing to malicious websites from such a system.
According to Trend Micro's technical notes, the malware targets systems running Windows 2000, Windows Server 2003, Windows XP, Windows Vista and Windows 7.
"Another possible attack scenario is when an attacker checks for websites powered by Apache Tomcat then attempts to access the Tomcat Web Application Manager," the Trend Micro researchers said. "Using a password cracking tool, cybercriminals are able to login and gain manager/administrative rights allowing the deployment of Web application archive (WAR) files packaged with the backdoor to the server."
In order to protect their servers from such threats, administrators should use strong passwords that cannot be easily cracked by using brute force tools, should deploy all security updates available for their systems and software and should avoid visiting unknown and untrusted websites, the Trend Micro researchers said.