The research revealed an increase from October 2019 onwards in brute force log-in attempts against routers, in which attackers use automated software to try common password combinations.
The number of attempts increased nearly tenfold, from around 23 million in September to nearly 249 million attempts in December 2019.
As recently as March 2020, Trend Micro recorded almost 194 million brute force logins.
“With a large majority of the population currently reliant on home networks for their work and studies, what’s happening to your router has never been more important,” Jon Clay, Director of Global Threat Communications for Trend Micro, said in a statement.
“Cybercriminals know that a vast majority of home routers are insecure with default credentials and have ramped up attacks on a massive scale. For the home user, that’s hijacking their bandwidth and slowing down their network. For the businesses being targeted by secondary attacks, these botnets can totally take down a website, as we’ve seen in past high-profile attacks.”
Another indicator that the scale of this threat has increased is devices attempting to open telnet sessions with other Internet of Things (IoT) devices.
Because telnet is unencrypted, it’s favoured by attackers — or their botnets — as a way to probe for user credentials.
At its peak, in mid-March 2020, nearly 16,000 devices attempted to open telnet sessions with other IoT devices in a single week, said the report titled “Caught in the Crossfire: Defending Devices From Battling Botnets”.
This trend is concerning for several reasons. Cybercriminals are competing with each other to compromise as many routers as possible so they can be conscripted into botnets.
These are then sold on underground sites either to launch Distributed Denial of Service (DDoS) attacks, or as a way to anonymise other attacks such as click fraud, data theft and account takeover, said the report.
To avoid such attacks, Trend Micro suggested several measures. It said that users should make sure the router is running the latest firmware.
Moreover, it is important to use a strong password and change it from time to time. The company urged users to check logs to find behaviour that does not make sense for the network.
Users should only allow logins to the router from the local network, it said.