A number of sharp eyed users on the security section of our BBS, have noticed that a number of Conexant based routers have ports open and visible on the Internet side of some router models. This has been known for some time with the Conexant based devices, but generally the firmware allows you to close the ports, or manufacturers release updates where the ports are only visible from the LAN side. Alas some routers have other ports that are still open, and via a telnet session it is possible to remotely reboot someones router. It is not just old models, it appears that the Zoom X5 router exhibits this behaviour.
If you have a Conexant based router and are not sure how to check whether it is affected, visit our Security section, where there are several threads now from various users of Conexant based hardware. It is generally possible to hide the ports, by port forwarding them to a non-existent IP address in the virtual server section of the router.
Finding out which ports are open on the Internet side of a router, is not that simple, but various on-line scanners exist that can help. Some sites that run port scanners are:
If you are running behind a NAT router, and have not set-up any port forwarding rules, then you should find all ports come back as either closed or stealth. If using a Conexant based router, you may see ports 21, 23, 80, 254 & 255 open, if any of these ports are open, then double check that you have WAN Side access disabled for these ports. One example is that on a Zoom X4 to disable port 80, you must access the Miscellaneous configuration screen and set WAN side HTTP server to 'disabled'. On an older AMX-CA61E router, you need to disable the HTTP, FTP and TFTP WAN side servers via the Miscellaneous configuration menu. After trying to close ports it is advisable to run the scans again.
Any reconfiguration of your router, or possible firmware upgrades are carried out at your own risk. If you are not aware whether you have a Conexant based router, or what actions to take visit our Security forum where other forum users will hopefully know the answer.
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