Security Experts:

Attackers Use Decade-Old Flaw to Target IoT Devices

Cybercriminals have been exploiting an old SSH vulnerability and insecure configurations to abuse Internet of Things (IoT) devices for attacks aimed at Web services and internal networks.

Millions of IoT devices have already been compromised and abused for distributed denial-of-service (DDoS) attacks and millions more are affected by critical vulnerabilities that make them an easy target for malicious actors.

While in many cases attackers hack IoT devices and leverage them to conduct attacks directly, researchers at Akamai have come across a different type of mass attack in which the compromised systems are used as proxies that route malicious traffic.

These attacks, dubbed by Akamai SSHowDowN Proxy attacks, have abused vulnerable CCTV, NVR, DVR, networking, storage and satellite antenna equipment to conduct HTTP-based credential stuffing campaigns. The breached devices are also used as an entry point to the internal networks that house them.

It is well known that many IoT devices have weak default administrator credentials, such as admin/admin or root/root. However, attackers are normally not able to use the admin account to connect to the device via SSH and execute commands.

On the other hand, if the device allows remote SSH connections, the attacker might be able to exploit a 12-year-old OpenSSH vulnerability (CVE-2004-1653) to enable TCP forwarding. In the attacks observed by Akamai, cybercriminals have used SSH options to create an SSH tunnel that makes it appear as if the attack traffic originates from the IP address of the compromised device.

Akamai pointed out that no new vulnerabilities are involved in SSHowDowN Proxy attacks. The problem is that many vendors ship their products with insecure default settings and users often don’t have the possibility to make configuration changes that would prevent attacks.

“While this has been reported before, the vulnerability has resurfaced with the increase of connected devices. Our team is currently working with the most prevalent device vendors on a proposed plan of mitigation,” Akamai said in its report.

As for mitigations, there are several steps that vendors could take to prevent the abuse of their products. Experts recommend disabling SSH by default, removing undocumented accounts, forcing users to change factory defaults, configuring SSH to disallow TCP forwarding, and providing a secure process for end-users to update configurations.

Users can secure their devices against potential attacks by changing default credentials, completely disabling the SSH service unless required for normal operation, and establishing inbound and outbound firewall rules to prevent unauthorized access.

Related: Mirai IoT Botnet Wasn't Alone in Massive DDoS Attack

Related: DDoS Attacks Are Primary Purpose of IoT Malware

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Eduard Kovacs (@EduardKovacs) is a contributing editor at SecurityWeek. He worked as a high school IT teacher for two years before starting a career in journalism as Softpedia’s security news reporter. Eduard holds a bachelor’s degree in industrial informatics and a master’s degree in computer techniques applied in electrical engineering.