Preventing denial of service attacks on an ADSL router

This content is 20 years old. I don't routinely update old blog posts as they are only intended to represent a view at a particular point in time. Please be warned that the information here may be out of date.

Since about April 2004, I’ve been having problems with my ADSL router at home (a Solwise SAR 110). As the hardware was just over 12 months old (and hence just out of warranty), the cynical side of me was resigned to the fact that it had just “broken”. Not wanting to lose my configuration settings through a firmware upgrade, I got used to resetting the router each day (sometimes several times a day) when it seemed to just drop off the network. Because I couldn’t access the box, I couldn’t check any logs and find out what was happening.

This all changed when I spotted a posting on my ISP’s support forum, directing me to Chris Marsh’s excellent SAR 110 and 130 Guide. Using Chris’ advice I have been able to stealth my router (as tested using the GRC Shields UP! port prober). The SAR Guide website also included interesting information on other configuration items that were not always clear from the Solwise manuals and help text.

Now that my router is no longer visible on the Internet, it seems to stay up as it did for the first year I was on ADSL (just under 13 days and counting as I write this). I can only assume that the problem was a denial of service (DoS) attack, that has now been prevented through the stealthing of the router.

Obviously, there are many types of router out there, but by following the same steps, it should be possible to stealth most ADSL routers, even if the user interface is slightly different.

4 thoughts on “Preventing denial of service attacks on an ADSL router

  1. McAfee also have an on-line security scanner at and there are a number of tests available from PC Flank. Beware though – some of these scanners use alarmist language to tell you that your system is insecure. I have a couple of ports that are deliberately open and just installing another firewall product (as suggested) won’t help me there!

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