Monday, August 13, 2018

Badness, Enumerated by Robots

A condensed summary of the blacklist data generated from traffic hitting bsdly.net and cooperating sites.

After my BSDjobs.com entry was posted, there has been an uptick in interest about the security related data generated at the bsdly.net site. I have written quite extensively about these issues earlier so I'll keep this piece short. If you want to go deeper, the field note-like articles I reference and links therein will offer some further insights.

There are three separate sets of downloadable data, all automatically generated and with only very occasional manual intervention.


Known spam sources during the last 24 hours

This is the list directly referenced in the BSDjobs.com piece.

This is a greytrapping based list, where the conditions for inclusion are simple: Attempts at delivery to known-bad addresses in domains we handle mail for have happened within the last 24 hours.

In addition there will occasionally be some addresses added by cron jobs I run that pick the IP addresses of hosts that sent mail that made it through greylisting performed by our spamd(8) but did not pass the subsequent spamassassin or clamav treatment. The bsdly.net system is part of the bgp-spamd cooperation.

The traplist has a home page and at one point was furnished with a set of guidelines.

A partial history (the log starts 2017-05-20) of when spamtraps were added and from which sources can be found in this log (or at this alternate location). Read on for a bit of information on the alternate sources.

Misc other bots: SSH Password bruteforcing, malicious web activity, POP3 Password Bruteforcing.

The bruteforcers list is really a combination of several things, delivered as one file but with minimal scripting ability you should be able to dig out the distinct elements, described in this piece.

The (usually) largest chunk is a list of hosts that hit the rate limit for SSH connections described in the article or that was caught trying to log on as a non-existent user or other undesirable activity aimed at my sshd(8) service. Some as yet unpublished scriptery helps me feed the miscreants that the automatic processes do not catch into the table after a manual quality check.

The second part is a list of IP addresses that tried to access our web service in undesirable ways, including trying for specific URLs or files that will never be found at any world-facing part of our site.

After years of advocating short lifetimes (typically 24 hours) for blacklist entries only to see my logs fill up with attempts made at slightly slower speeds, I set the lifetime for entries in this data set to 28 days. The background including some war stories of monitoring SSH password groping can be found in this piece, while the more recent piece here covers some of the weeding out bad web activity.

The POP3 gropers list comes in two variations. Again lists of IP addresses caught trying to access a service, most of those accesses are to non-existent user names with an almost perfect overlap with the spamtraps list, local-part only (the part before the @ sign).

The big list is a complete corpus of IP addresses that have tried these kinds of accesses since I started recording and trapping them (see this piece for some early experience and this one for the start of the big collection).

There is also a smaller set, produced from the longterm table described in this piece. For much the same reason I did not stick to 24-hour expiry for the SSH list, this one has six-week expiry. With some minimal scriptery I run by hand one or two times per day, any invalid POP3 accesses to valid accounts get their IP adresses added to the longterm table and the exported list.

If you're wondering about the title, the term "enumerating badness" stems from Marcus Ranum's classic piece The Six Dumbest Ideas in Computer Security. Please do read that one.

Here are a few other references other than those referenced in the paragraphs above that you might find useful:

The Book of PF, 3rd edition
Hey, spammer! Here's a list for you! which contains the announcement of the bsdly.net traplist.
Effective Spam and Malware Countermeasures, a more complete treatment of those keywords

If you're interested in further information on any of this, the most useful contact information is in the comment blocks in the exported lists.

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