Last year I wrote about a couple of network security projects which were in their early stages of development. As the last of these has recently completed, I thought it might be useful to summarise their outcomes.
We have had edge filtering in place for a long time, since we ran Solaris on Suns in fact, configured automatically from our machine configuration system (lcfg). This has proved to be very successful in practice. Our main edge routers typically reject a couple of million bogus packets per day, though this is still rather less than 0.5% of their total throughput. We mostly don’t log this in detail, as there’s just too much of it and most of it isn’t very interesting, but we do have a couple of externally-visible machines which log more extensively. These show several thousand scans per day, mostly for various Microsoft services, against individual IP addresses which have not been in use for several years.
The first of the projects I mentioned was “Scanning for Compromised Machines“. After some investigation of our own, we learned that the University would be buying in to the ESISS scanning tool. We now have this in use, regularly scanning all machines (managed and self-managed) with open firewall holes. This has proved to be reasonably successful, and has thrown up a number of cases for further investigation. Where these are with self-managed machines, we follow up with the machine’s manager to have any vulnerabilties closed down.
The other project was a pilot Intrusion Detection System. This was a useful exercise, and the experience gained will certainly be helpful if we do later implement this as a full service, though overall the result was rather less useful than the “Scanning” project for reasons which are listed in more detail in the report. In summary, though, the reports it produces are rather noisy due to our heterogeneous environment, and the rules we use are a couple of weeks or so behind the leading edge so we tend to hear about (and patch!) vulnerabilities through other routes before they start to show in the reports. We’ll leave the pilot system running, so long as it doesn’t interfere with the proper functioning of our network, but there would still be quite a bit of work required to bring it up to production standard, and that effort just isn’t available at the moment as a result of the SL7 upgrades and the Appleton Tower decant.