Botnet
Botnet activity warning
A bit of advice from the folks at the CBL, posted with permission and some light editing. I’ve been seeing some folks report longer connection times at some places, and this might explain some of it. It’s certainly possible, even likely, that the large ISPs are getting a lot of this kind of traffic.
A botnet, likely a variant of cutwail, has been for the past several years been specializing in using stolen credentials, doing port 25/587 SMTP AUTH connections to the spoof’d users server, and attempting to relay thru the connection to elsewhere. They will also, in some cases, attempt to log into the MX IP using a brute force attack against the email address. Other miscreants try the same thing with IMAP or POP or even SMTPS.
If they manage to compromise an email account, they use the account to send spam. For corporate accounts they can steal employee identities, request wire transfers, and send out corporately authenticated spam. If they get it, game over, the whole account is compromised and they can and do wreak havoc.
This has been going on for a couple of years, and now is the largest volume of spam from botnets. Cutwail is not the only botnet doing AUTH attacks, but appears to be the most prolific. Attacking POP and IMAP appears to be more recent, and is more related to spear-phishing (spamming executives) and other bad things.
In the last month or two, the behavior has changed a bit. The infections are trying to establish as many connections simultaneously as it can get away with. This is similar behavior to ancient or unpatched versions of qmail. This is swamping some servers by tying up a significant number (or even all) of the TCP sockets available.
The CBL is recommending that folks check their mail servers. If the mail server has a “simultaneous connection per IP limit”, it should be set to some limited number. If it’s not set then set it. Otherwise, your server is at risk for being unable to handle real mail. Make sure your IMAP and POP are secured as well as they are being targeted, too.
The XBL can also help with this. But securing your server is the first step.
Malicious email terms defined.
Legitimate mailers need to distinguish themselves from spammers. One important piece of that is knowing what spammers do. SendGrid has put together some information on common scams and techniques spammers use to get email delivered.
Some of these terms, like doxxing and swatting, are not specifically email related. However, they are used against people who are fighting abuse on the Internet. People who are actively investigating darker portions of the internet face real danger. Brian Krebs has made some of the harassment he’s received public. I know other people in the space have been harassed but don’t make it so public.
I think it’s valuable for marketers to understand the malicious and criminal end of mail. It makes some filtering decisions less random when you know the types of bad traffic that the filters are trying to stop. The SendGrid document is a fantastic first stop to learn about them.
Botnet herder / spam kingpin arrested
Via Krebs on Security, a russian named Pyotr Levashov has been arrested in Spain. According to news reports (NY Times, Reuters) the arrest happened in response to a warrant issued by the US, but no details were given as to what he was being charged with. The DoJ says the case is currently under seal and will not comment on charges.
There is widespread agreement that this person is involved in major spamming operations. He’s one of Spamhaus’ Top 10 spammers (ROKSO listing). He’s been implicated in fraud during the 2012 elections in Russia. Some reports are speculating that he was involved in the hacking of the 2016 elections here in the US, but there’s no current evidence that’s true.
March 2017: The Month in Email
It’s that time again… here’s a look at our last month of blog posts. We find it useful to recap each month, both to track trends and issues in email delivery and to provide a handy summary for those who aren’t following along breathlessly every single day. Let us know if you find it useful too!
As always, I wrote about email filters. It’s so important to recognize that filters aren’t arbitrary — they’re detailed instructions that help meet specific user needs, and the more you are cognizant of that, the better you’ll be able to work with them. Additionally, filters aren’t perfect and likely never will be. False positives and false negatives are frustrating, but as long as spam is still a viable business for spammers, they’ll continue to figure out how to work around filters. As such, we can’t expect filters to be 100% accurate in determining what constitutes wanted and unwanted mail.
Part of this, of course, is due to the problem of fraudulent signups. Companies aren’t particularly vigilant about address acquisition and hygiene, and as a result, they’ll claim you “signed up” for their email when you did not. Some people believe that a confirmed opt-in (COI) will solve this problem, but our experience is companies are reluctant to leave revenue on the table, and that they will continue to mail to addresses that have not confirmed.
Address sharing and co-reg is also part of the problem. As we saw in the extensive RCM data breach, many major brands continue to work with third-party senders to send mail in ways that are quite clearly spam. And in more criminal activity, I looked at the rise of botnets and how some of those criminals were brought to justice. In other justice news, there’s been an indictment in the Yahoo breach and another CASL enforcement action.
I wrote a post about bounce handling and “relaying denied” error messages, which are quite rare. It’s useful to have an understanding of these and other error messages, since bounces are sometimes indicative of a larger technical issue, such as when AOL accidentally bounced all messages for a short period last week. Speaking of AOL, we noted that there’s no official timeline for the move from Verizon addresses to AOL addresses following the 2015 acquisition, but it may be worth considering asking your customers to update their addresses.
Spam and filters aren’t the only factors of course. It can be challenging to figure out the multiple factors that make up the black box of delivery. And of course, the most important part of delivery continues to be engagement, engagement, engagement.
I wrote a few posts this month on why I do what I do, and why it’s so important to me. First, I wrote about A Day Without A Woman, and my choice not to participate in offering advice and guidance for that day. The truth is that I enjoy sharing what I know and helping people solve problems. I was honored to be named one of 11 Innovators in Email, and I know that my volunteer work in the industry and my unpaid blogging work is a big part of that. It may sound corny, but I really do believe we are on the front lines of the fight of good vs. evil online, and despite the distractions of politics and world events, we must all continue to do our part.
What about the botnets?!
Botnets are a huge problem for a number of reasons. Not only are they used to send spam, they’re also used in criminal activities. One of the major challenges in dealing with botnets is finding and stopping the people who create and use them. Why? Because the internet is global and crime tends to be prosecuted within local jurisdictions.
Following the SMTP rules
An old blog post from 2013, that’s still relevant today.
“Blocked for Bot-like Behavior”
An ESP asked about this error message from Hotmail and what to do about it.
“Bot-like” behaviour usually means the sending server is doing something that bots also do. It’s not always that they’re spamming, often it’s a technical issue. But the technical problems make the sending server look like a bot, so the ISP is not taking any chances and they’re going to stop accepting mail from that server.
If you’re an ESP what should you look for when tracking down what the problem is?
First make sure your server isn’t infected with anything and that you’re not running an open relay or proxy. Second, make sure your customers aren’t compromised or have had their accounts hijacked.
Then start looking at your configuration.
HELO/EHLO values
Port25 blocking
A number of hosting providers are blocking outgoing port25. This has implications for a lot of smaller senders who either want to run their own mail server or who use SMTP to send mail to their ESP.
CASL botnet take down
The CRTC served its first ever warrant as part of an international botnet takedown. The warrant was to take down a C&C (command and control) server for Win32/Dorkbot. International efforts to take down C&C servers take a lot of effort and work and coordination. I’ve only ever heard stories from folks involved but the scale and work that goes into these take downs is amazing.
Bots are still a problem. Even if we manage to block 99% of the botnet mail out there people are still getting infected. Those infections spread and many of the newer bots steal passwords, banking credentials and other confidential information.
This kind of crime is hard to stop, though, because the internet makes it so easy to live in one country, have a business in a third, have a shell corp in a fourth, and have victims in none of those places. Law enforcement across the globe has had to work together and develop new protocols and new processes to make these kinds of takedowns work.
What happened with the CBL false listings?
The CBL issued a statement and explanation for the false positives. Copying it here because there doesn’t seem to be a way to link directly to the statement on the CBL front page.
Increase in CBL listings
Update: As of Nov 24, 2015 11:18 Pacific, Spamhaus has rebuilt the zone and removed the broken entries. Expect the new data to propagate in 10 – 15 minutes. Delivery should be back to normal.
The CBL issued a statement, which I reposted for readers that find this post in the future. I think it’s important to remember there is a lot of malicious traffic out there and that malicious traffic affects all of us, even if we never see it.
Original Post from 10am pacific on Nov 24
Mid-morning west coast time, I started seeing an uptick in reports from many ESPs and marketers that they were getting listed on the XBL/CBL. Listings mentioned the kelihos spambot.
Are botnets really the spam problem?
Over the last few years I’ve been hearing some people claim that botnets are the real spam problem and that if you can find a sender then they’re not a problem. Much of this is said in the context of hating on Canada for passing a law that requires senders actually get permission before sending email.
Botnets are a problem online. They’re a problem in a lot of ways. They can be used for denial of service attacks. They can be used to mine bitcoins. They can be used to host viruses. They can be used to send spam. They are a problem and a lot of people spend a lot of time and money trying to take down botnets.
For the typical end user, though, botnets are a minor contributor to spam in the inbox. Major ISPs, throughout the world, have worked together to address botnets and minimize the spam traffic from them. Those actions have been effective and many users never see botnet spam in their inbox, either because it’s blocked during send or blocked during receipt.
Most of the spam end users have to deal with is coming from people who nominally follow CAN SPAM. They have a real address at the bottom of the email. They’re using real ISPs or ESPs. They have unsubscribe links. Probably some of the mail is going to opt-in recipients. This mail is tricky, and expensive, to block, so a lot more of it gets through.
Much of this mail is sent by companies using real ISP connections. Brian Krebs, who I’ve mentioned before, wrote an article about one hosting company who previously supported a number of legal spammers. This hosting company was making $150,000 a month by letting customers send CAN SPAM legal mail. But the mail was unwanted enough that AOL blocked all of the network IP space – not just the spammer space, but all the IP space.
It’s an easy decision to block botnet sources. The amount of real mail coming from botnet space is zero. It’s a much bigger and more difficult decision to block legitimate sources of emails because there’s so much garbage coming from nearby IPs. What AOL did is a last resort when it’s clear the ISP isn’t going to stop spam coming out from their space.
Botnets are a problem. But quasi legitimate spammers are a bigger problem for filter admins and end users. Quasi legitimate spammers tend to hide behind ISPs and innocent customers. Some send off shared pools at ESPs and hide their traffic in the midst of wanted mail. They’re a bigger problem because the mail is harder to filter. They are bigger problems because a small portion of their recipients actually do want their mail. They’re bigger problems because some ISPs take their money and look the other way.
Botnets are easy to block, which makes them a solved problem. Spam from fixed IPs is harder to deal with and a bigger problem for endusers and filters.
Whirlwind that is M3AAWG
It’s been a great conference, and it’s only about half done. As is common at these conferences, I write down lots of things we should do and need to publish. The difference is now that we are growing I may have the time to put the polish on them and get them published.
Today’s keynote discussed the economics of botnet mitigation. Michel van Eeten from Delft University of Technology presented information compiled from some different datasets about botnets.
Good news
Botnet infection rates are relatively stable. They’ve not spiraled out of control like some people were predicting.
Interesting news
More than 50% of bot infections are contained on 50 ISPs in the entire world.
Bad news
Centers set up specifically to fix botnet infections don’t really have a big impact on infection cure rate.
Good news
ISP actions and walled gardens do have an impact on infection cure rates.
The biggest take away from the session is that ISPs are critical in both protecting from infection and helping users cure infection once it happens.
"Blocked for Bot-like Behavior"
An ESP asked about this error message from Hotmail and what to do about it.
“Bot-like” behaviour usually means the sending server is doing something that bots also do. It’s not always that they’re spamming, often it’s a technical issue. But the technical problems make the sending server look like a bot, so the ISP is not taking any chances and they’re going to stop accepting mail from that server.
If you’re an ESP what should you look for when tracking down what the problem is?
First make sure your server isn’t infected with anything and that you’re not running an open relay or proxy. Second, make sure your customers aren’t compromised or have had their accounts hijacked.
Then start looking at your configuration.
HELO/EHLO values
Another one bites the dust
NASK (the Polish domain registry) has taken over a number of domain names used in spreading viruses and infections.
Read MorePhones part of SMS botnet
Spammers have been moving into the phone market for a long time. Just recently security firms have discovered an Android botnet. This botnet sends viruses over SMS, and when a link in the SMS is clicked, the phone is infected with the virus which then sends more SMS.
The technology for blocking and reporting SMS spam is comparable to email blocking technology 10 or 12 years ago. There just aren’t many tools for people to use to control this spam. M3AAWG is addressing mobile spam, but it still seems that the volumes are increasing without much recourse. Even the 7726 reporting number doesn’t seem to stop the spam (nor remove per-text charges).
At least in the beginning of the email spam problem, we didn’t have botnets. Now, at the beginning of the curve for SMS spam, we already have self replicating botnets. I’m afraid the good guys might be behind on this issue.
Then again I might just be cranky because SMS spammers woke us up at 4:30 am.
Infoworld article
TNW article
PCWorld article
Cloudflare and Spamhaus
Spamhaus has been the subject of a lot of discussion the last few weeks. I touched on this a little in June when I blogged that a number of large brands were getting SBL listings.
But big brands are not the only companies with publicly discussed SBL listings.
Cloudflare, the content delivery network that grew out of project honeypot, has a number of SBL listings, covering at least 2 /18s and a /20. Representatives and customers of Cloudflare have been discussing the listings on twitter.
As a content provider, Cloudflare isn’t actually sending mail nor are they actually hosting the content. What they are doing is providing consistent name service and traffic routing to malicious websites. In fact, they’ve been providing services to a malware botnet controller (SBL138291) since May, 2012. They’re also providing services to a number of SEO spammers. Both of these actions are justification for a SBL listing, and Spamhaus has a history of listing providers protecting spammers.
Cloudflare claims they take action on all “properly filed complaints” and they may actually do that. But their reports require quite a bit of information and require consent for releasing information to 3rd parties. Looking at the website, it appears to me to be a site designed to discourage abuse reports and stop people from reporting problems to Cloudflare.
When you look at the Cloudflare business model it’s clearly one that will be abused. Cloudflare acts as a reverse proxy / pass through network that caches data from their customers. This protects the abusers webhosting setup and prevents people tracking the abuser from being able to determine the true host of a website. As a responsible internet citizen, Cloudflare should be disconnecting the customers hiding behind Cloudflare’s services.
Unfortunately, Cloudflare seems unwilling to actually police their customers. They’ve taken a totally hands off approach.
Let’s be frank. Cloudflare has been providing service to Botnet C&C servers for at least two months. It doesn’t matter that the abuser has the malware on a machine elsewhere, Cloudflare’s IP is the one that serves the data. I don’t care what you think about spam, providing service to malware providers is totally unacceptable. It’s even more unacceptable when you claim to be a security company. Nothing about malware is legitimate and the fact that Cloudflare is continuing to host a malware network command and control node is concerning at the very least.
Cloudflare (.pdf) is listed on Spamhaus for providing spam support services. The most obvious of these is providing service to a malware controller. And Spamhaus escalated the listings because they are allowing other abusers to hide behind their reverse proxy.
DNS Changer servers going offline
There are a whole host of different botnets. One botnet run by Rove Digital infected computers with viruses that changed their DNS settings, giving the botnet runners the ability to control how the infected computers viewed the Internet.
The criminals behind the DNS Changer virus were arrested in November of last year. The court ordered the Internet Systems Consortium (ISC) to operate replacement DNS servers for computers infected with the botnet viruses in order to give users a chance to clean and fix their computers.
That court order expires on Monday.
Anyone who is still infected with the DNS Changer malware will see their internet services greatly curtailed when the DNS servers go offline.
If you run Windows and you haven’t yet checked to see if you’re infected, you should do so soon. There are a number of websites you can visit that will tell you if you are actually infected with the DNS changer virus and if you are will give you information on how to fix your system.
Anti-Botnet Code of Conduct Published
The Communications Security, Reliability and Interoperability Council (CSRIC) published a Anti-botnet code of conduct for ISPs. This is a purely voluntary code for U.S. ISPs that want to mitigate the botnet threat to follow. You can download a full copy of the final report from the MAAWG website. The FCC has published a fact sheet about the report on their own website.
Read MoreMore on Rove Digital
Brian Krebs has more on Rove Digital and the criminal connection to other scammers and spammers.
Read MoreBiggest botnet takedown to date
Yesterday law enforcement officials arrested 6 people and charged them with running a massive internet fraud ring. Over 4 million PCs were part of the botnet.
According to the FBI
Uptick in botnet spam
There’s been a heavy uptick in botnet spam over the last few days, judging by things I’m hearing and my own mailboxes. There are a few common subject lines, but all of them are trying to get recipients to either run programs or visit malicious web pages.
The first subject line I’m seeing a lot of is “<name> wants to be friends with you on facebook!” In my mailbox most of those names have not been common European names. The give away that this isn’t actually a Facebook invite is the Reply-To address pointing to Linkedin. The URLs in the message appear to be random strings of numbers, and may actually encode recipient information in them.
The second has a subject that that is a variation on “End of July Statement.” The spammers are mixing capitals, adding in “Re:” and “FWD:” and sometimes increasing the urgency by adding required or STAT!! to the mail. These mails contain a .zip file which probably contains some virus which will turn the recipient machine into the next spam spewing bot.
The third variation has the subject line “Uniform Traffic Ticket.” The content is a citation that tells the recipient they were speeding somewhere in New York (possibly other states, I have only done a spot check of the couple hundred copies I have). There is, however, a .zip attachment with a virus.
Most people probably aren’t seeing these. SpamAssassin is doing a reasonably good job here of catching the spam and filtering it. I’m sure that the bigger ISPs are also filtering it effectively. But one person did forward a copy of the spam to a mailing list and ask if anyone knew what was going on.
If you get any of these messages, you don’t need to ask. It’s virus spam. Don’t open it and don’t forward it.
News about the Rustock takedown
Spam levels plummeted 2 weeks ago as the Rustock botnet was beheaded. Reports have been trickling out in the press about the takedown, about the botnet and about the team responsible.
Rustock Takedown Analysis at The Register
Brian Krebs’ intitial report of the takedown
Taking down botnets from a Microsoft attorney
Spam Network Shut Down at the Wall Street Journal
Global Spam Levels Graph from Symantec