On January 14, 2026, global telnet traffic observed by GreyNoise sensors fell off a cliff. A 59% sustained reduction, eighteen ASNs going completely silent, five countries vanishing from our data entirely. Six days later, CVE-2026-24061 dropped. Coincidence is one explanation.
The pattern points toward one or more North American Tier 1 transit providers implementing port 23 filtering
Telnet is still a quick and easy way to check if a certain port on a machine is listening.
But that’s not what it was made for, of course. It’s real meaning has gone down long ago.
Can do
ncnow which is more flexible for connectivity tests.