Fighting "Snowshoe" Spam

Today Spamhaus announced they are releasing a new list of IP addresses from which they've been receiving "snowshoe" spam — unsolicited email distributed across many IPs and domains in order to avoid triggering volume-based filters. "This spam is sent from many small IP ranges on many Internet Service Providers (ISPs), using many different domains, and the IPs and domains change rapidly, making it difficult for people and places to detect and block this spam. Most importantly, while each host/IP usually sends a modest volume of bulk email, collectively these anonymous IP ranges send a great deal of spam, and the quantities of this type of spam have been increasing rapidly over the past few months." A post at the Enemies List anti-spam blog wonders at the impact this will have on email service providers and their customers. The author references a conversation he had with an employee from one of these providers: "... I replied that I expected it to mean the more legitimate clients of the sneakier gray- and black-hat spammers would migrate to more legitimate ESPs — suggesting that it was, in the long run, a good thing, because ESPs with transparency and a reputation to protect will educate their new clients. His reply was essentially that this would be a problem for them in the short run, because it would swamp their new customer vetting processes and so on."

Comments

I represent that!

[Anonymous Coward]

As a Canadian I figured I'd better look that up.

http://www.spamhaus.org/faq/answers.lasso?section=Glossary#233

Like a snowshoe spreads the load of a traveler across a wide area of snow, snowshoe spamming uses many frequently-changing IP addresses, domains and aliases to spread out the spam load in order to dilute recipient reputation metrics and evade filters. Snowshoers use many fictitious business names (DBAs), fake names and identities, and frequently changing postal dropboxes and voicemail drops. Conversely, legitimate mailers try hard to build their brand reputation based on a real business address, a known domain and a small permanent range of sending IPs. Snowshoers often use anonymized or unidentifiable whois records, whereas legitimate senders are proud to provide their bona fide identity.

Some showshoers use tunneled connections from their back-end spam cannon to the spam egress IP. The back-end IP address is not in the spam headers. ISPs, you are in a position to detect those back-end spam cannons by checking where traffic flows are coming from. Remember, the tunneled connection is not necessarily on port 25. Spamhaus always appreciates such information.

Greylisting!

[erroneus]

Okay okay! I heard you all the last time I brought it up. But the results are simply awesome. And greylisting is perfect against these snowshoe distribution methods. The downside might be the database filling up.

Re:Greylisting!

[aztracker1]

Then the senders' mail servers are broken, and don't deserve to have their mail read. Greylisting is perfectly acceptable, however it is slightly less than effective as more and more bots will actually retry.

Re:Greylisting!

[jackbird]

it is important to note that "longer than normal" can mean 24 or more hours for a surprisingly large number of mail servers. Forum registrations and the like are particularly frustrating.

Re:Snowshoe?

[djupedal]

Would you prefer: u e d a m IP a d i o t a t v b f

unsolicited email distributed across many IPs and domains in order to avoid triggering volume-based filters.

Snowshoe: spam not ordinarily wanted sent hourly occupying email

Re:How is this different

[Anonymous Coward]

from the typical spambot? Any big enough botnet dedicated to send spam could have millons of nodes.

Of course, most of those nodes are located in residential IP ranges, not meant to have mail servers usually. There are blacklists for that since a lot ago. That combined with greylisting (some spambots can handle greylistings, some not), and content filtering could reduce a lot the impact of that kind of spam.

It's completely different. Snowshoe spam does not come from infected PCs (proxies or bots), it comes from *static* IP addresses *bought* by the spammers from ISPs. The spammers have been buying IP ranges, class Cs, directly from ISPs and filling these ranges with 'nonsense' domains, each one sending 'a bit' of spam is order to spread the load across the whole class C to lessen complaints.

Re:Snowshoe?

[martin-boundary]

wish all the PCs that have bots running on them would just blowup.. or like the good ole day viruses; just wipe out the drives.. .eeh..

Blame Evolution. A virus that messes too much with the host PC has a low survival rate. The most successful viruses don't do too much damage, as that keeps them a low priority with AV software, and don't cripple the infection vectors, as that helps them spread, and aren't too OS specific, as that allows them to tolerate service packs and software upgrades.

Re:I have a fine idea

[X0563511]

I think a better idea...

Stop filtering spam at all. For a whole week.

Let the spammers break the system.

Re:Snowshoe?

[ozmanjusri]

Blame Evolution.

Evolution?

More likely Outlook and the colander-like OS it runs on.

Re:Snowshoe?

[jonadab]

> unsolicited email distributed across many IPs and domains
> in order to avoid triggering volume-based filters.

I hereby propose we just call it "spam" and have done.

I mean, seriously, is anybody really still worried about the old-fashioned kind of spam that was sent back in the early nineties, going out from one mail server with one IP for months on end, using an actual valid return email address from an actual valid domain owned by the senders? Have you *received* any of that lately?

I haven't. Near as I can tell, *all* modern spam is sent by a collection of nodes distributed across many IPs on many subnets and randomly generates a new forged sender address for each message. We don't need a special name specifically for spam that's sent like that. If you just say "spam", that communicates the whole idea. Everybody who has been paying attention knows that it's sent in the described fashion these days.