Wednesday, May 21, 2008

Fake Address Round Trip Time: 13 days

The results are in. Our adversaries really are mindless automata.

Regular readers will have noticed that I've been running a small scale experiment over the last few months, feeding one spammer byproduct back to them via a reasonably accessible web page. The hope was that I would learn a few things about spammer behavior in the process.

After collecting fake addresses in my domains generated elsewhere for a while, I started noticing that a short time after I'd put addresses on the traplist page, they would start appearing as To: addresses on what appeared to be spam message entries in my logs. After a while more, I was certain that the round trip time was down to a few days, but my notes did not include exact dates for when each individual harvested address made it into my spamtrap list. Meaning, of course, I had no way of telling just how fast the process is.

Time to cheat slightly, or, as they say in the trade, perform a controlled experiment. Instead of sticking to the original plan of strictly collecting addresses generated elsewhere and feed them back to the harvesters via the web page, I decided to deviate slightly and plant an address at a specified date, and maybe add another few for data points later. I did the obvious thing and on October 11th, 2007, I slipped into one of that day's batches of collected addresses.

Needless to say, my attention wandered from the project in the meantime. After all, in October there was still that book to finish, and after the book was done, other developments had my attention or at least drained my energy for quite a while. So it was only last Sunday it struck me that by now I should have at least some data on what actually happened. One other reason it was suddenly quite appropriate to sum up the data was that the domain had been turned over to new owners, and it will likely move out of my sphere of responsibility in the near future.

So here's the result, the fake address round trip time:

$ grep /var/log/spamd
Oct 24 03:40:40 skapet spamd[20795]: (BLACK)
<> -> <>

That is, the first time my artificially inserted address was used as a spam target was thirteen days after I put it on the traplist page. Since then, something, somewhere, has tried

$ grep -c /var/log/spamd

to deliver email to our imaginary friend a total of 300 times. Data taken from the spamd in front of that domain's secondary mail exchanger, of course. As always, I would love to hear from you about any related experiences.

In upcoming columns we will see, er, actually I find myself with such a selection of tempting topics to choose from, it is really hard to decide what to cover next. But the next one will appear here shortly.

Update 2015-08-01: In a totally unrelated article, posted on the afternoon of July 24th, 2015, the string appeared. it took only three days, two hours and forty-eight minutes (approximately) before my spamd(8) logged this attempt at delivering mail to that address:

Jul 27 20:16:01 skapet spamd[1520]: (GREY) <> -> <>

Thanks to the script that also prepares the downloadable list of trapped IP addreseses, I was alerted of this happening, and the address was duly added to the spamtraps list and the accompanying web page as part of the batch that took the list to its current count of 29135 entries.

From this accidental anecdotal evidence, we can conclude that the time from when random string containing an at sign appears on a web site to the time it's used as spam target has now shrunk to about three days.

The attempts seem to be a little less energetic this time though: greping the relevant logs turns up only 27 attempts at delivery. It's possible this is down to the fact that there are now so many more imaginary friends to choose from in that long list.

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