Cisco PSIRT has contacted customers to describe an evolution in attacks against Cisco IOS Classic platforms. Cisco has observed a limited number of cases where attackers, after gaining administrative or physical access to a Cisco IOS device, replaced the Cisco IOS ROMMON (IOS bootstrap) with a malicious ROMMON image.
In all cases seen by Cisco, attackers accessed the devices using valid administrative credentials and then used the ROMMON field upgrade process to install a malicious ROMMON. Once the malicious ROMMON was installed and the IOS device was rebooted, the attacker was able to manipulate device behavior. Utilizing a malicious ROMMON provides attackers an additional advantage because infection will persist through a reboot.
No product vulnerability is leveraged in this attack, and the attacker requires valid administrative credentials or physical access to the system to be successful. The ability to install an upgraded ROMMON image on IOS devices is a standard, documented feature that administrators use to manage their networks. No CVE ID will be assigned.
The Cisco PSIRT has recently updated a number of technical documents to include information regarding the ROMMON attack as well as other threats to Cisco IOS devices. The following white papers are publicly available and provide information for preventing, detecting, and remediating potential compromise on Cisco IOS devices.
Cisco recommends users of Cisco IOS devices review these documents to understand the types of threats against Cisco IOS devices. Cisco also recommends users ensure operational procedures include methods for preventing and detecting compromise.
For help with implementing any of the recommendations in the documents, customers should contact their appropriate support organization.
We request your assistance by distributing this information to your constituent organizations to raise awareness about the evolution of threats against Cisco IOS devices.
For questions regarding information in the above documents, contact firstname.lastname@example.org.