Cisco alerts users to password-spraying attacks targeting VPN services

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Networking giant Cisco has warned its users of an ongoing attack against its business VPN services.

In a security advisory, Cisco said it had been notified of an ongoing password-spraying attack against different third-party VPN concentrators.

In this instance, it was Remote Access VPN (RAVPN) services configured on Cisco Secure Firewall that were affected.

Russian attackers

“Depending on your environment, the attacks can cause accounts to be locked, resulting in Denial of Service (DoS)-like conditions,” Cisco explained, saying that the activity appears to be a reconnaissance effort. The threat actors were not named.

Password spraying is a type of attack in which the threat actor tries the same password with multiple accounts, until one combination works.

Listing its set of defenses and mitigations, Cisco recommended enabling logging to a remote syslog server for improved correlation and auditing of network and security incidents across various network devices; securing default remote access VPN profiles by pointing unused default connection profiles to sinkhole AAA servers; leveraging TCP shun to manually bloc dangerous IP addresses, configuring control-place ACLs to block unauthorized public IP addresses from running VPN sessions; and using certificate-based authentication for RAVPN.

Security researcher Aaron Martin claims the attack was likely the work of an undocumented malware botnet named Brutus.

He made the connection after observing the malware’s targeting scope and attack patterns, it was said. In his analysis of the botnet, Martin said it counts some 20,000 IP addresses worldwide. At first, the attacks targeted SSLVPN appliances from Fortinet, Palo Alto, SonicWall, and Cisco, but have since evolved to include web apps using Active Directory for authentication, too.

To avoid raising any flags, Brutus rotates its IPs every six attempts.

Although inconclusive, some evidence points to Brutus being the work of APT29, an infamous Russian state-sponsored threat actor.

Via BleepingComputer