If you have one of these old Asus routers, update its firmware as it may have a critical vulnerability that 'may allow remote attackers to gain unauthorized access'
If you've got an old Asus router, you might want to check whether it's needing a firmware update. Asus has just reported that three of its older DSL modem routers have a critical vulnerability, an "authentication bypass vulnerability" that "may allow remote attackers to gain unauthorized access into the affected system."
Asus hasn't just dropped that bombshell and left the room, though; there's a firmware update you can install to patch the vulnerability. The affected models are the DSL-AC51, DSL-N16, and DSL-AC750, and here are links to the firmware you should install for each of these:
The firmware you want is the latest one, version 1.1.2.3_1010. You download this firmware, and then upload it to your router's firmware upgrade page.
For instance, for the AC51, after downloading and unzipping the file on a PC connected to the router, you go to your router's administration page and navigate to Advanced Settings > Administration > Firmware Upgrade, then select Browse in the New Firmware File field, and click Upload. It will reboot when it's done.
These three affected routers are all getting on a bit now— each is listed as an EOL product on Asus' site. Older devices tend to be more at risk of becoming vulnerable to security issues, so it's not a massive surprise that old routers like these can be discovered vulnerable to such critical security flaws.
Even if you don't have one of these routers, critical security vulnerabilities can act as a good reminder to keep our routers updated. I don't know about you, but router updates aren't something I tend to keep on top of. Many will update automatically, but it can't hurt to check every now and then—I'm saying this to hammer it into my own head, more than anything.
In fact, it's probably a good idea to do the rounds on updates every now and then: Windows updates, graphics drivers, router, and software. You never know when it might catch something critical.