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.
 

Related Posts

Browsers, security and paranoia

MAAWG is coming up and lots of us are working on documents, and presentations. One of the recent discussions is what kind of security recommendations, if any, should we be making. I posted a list of things including “Don’t browse the web with a machine running Windows.”
Another participant told me he thought my recommendation to not use a windows machine to browse the web was over the top and paranoid. It may be, but drive by malware attacks are increasing. Visiting big sites may not be enough to protect you, as hackers are compromising sites and installing malware to infect visitors to those sites. Some ad networks have also been used to spread malware.
Criminals have even figured out how to install malware on a machine from email, without the recipient having to click or open attachments.
Avoiding the internet from a machine running Windows is a security recommendation I don’t expect many people to follow, but I do not think security and anti-virus software is enough to protect people from all of the exploits out there.
Of course, there are a lot of reasons that one might be forced to use a particular browser or operating system. For instance, I was on the phone with my bank just today to ask if they supported Safari. They say they do, but there are some things that just don’t work. The customer service rep said that they recommend Internet Explorer to all their users. She then suggested I switch browsers. No thanks, I’ll deal with the broken website.
Compromises are a major threat, and criminals are spending a lot of time and money on creating ways to get past current security. No longer is “not clicking on malware” enough to protect users. When a security clearinghouse is compromised and used as a vector for a targeted attack against Google, none of us are safe. When a security company is compromised, none of us are safe.
I realize my recommendation to avoid browsing the web on a Windows based machine is more wishful thinking than practical. I also know that other browsers and operating systems will be targeted if enough people move away from currently vulnerable operating systems. And I know that a simple, offhand suggestion won’t fix the problem.
As someone who’s been online long enough to see the original Green Card spam I know that online dangers evolve. But I can’t help thinking that most of us aren’t taking the current threats seriously enough.

Read More

GDPR and Whois data

For folks who aren’t following the discussion about whois records and GDPR compliance there’s a decent summary at vice.com: What Is Going to Happen With Whois?

Read More

Anatomy of a successful phishing attempt

Earlier this year the Exploratorium was the victim of a phishing attack. They’ve posted an article on what happened and how they discovered and dealt with the issue.
But they didn’t just report on the attack, they dissected it. And, as is appropriate for a organization with a mission of education, they mapped out what they discovered during the investigation.

There are a couple of things that stand out to me about this attack. One is that of the more interesting pieces to me is that there was a delay between the compromise and the start of the attack. The Exploratorium calls it “the pivot” and describes it as the hacker deciding what to do next. The second is that the phisher actively interacted with the victim’s account. All new mail was sent to the trash automatically so she wouldn’t see incoming mail. Some mail was actively replied to so more people would click on the message. The phisher took steps to retain access to the account for as long as possible.
One thing that the Exploratorium didn’t see was any actual access to Exploratorium files or information. That may be because the Exploratorium itself wasn’t the target. Once a phisher / hacker has access to the email account, they have access to almost everything in your online life: calendars, bank accounts, credit accounts, the list goes on. Email addresses are our online identity and getting access to the address can open access to so much more.
Quite frankly it can happen to any of us. Earlier this week we received a phishing message that looked very plausible. It came from a law firm, mentioned a subpoena and even had an attachment personalized to our company. The attachment wasn’t opened so we were fine, but I can see how that kind of email might trick someone into getting infected.
We all need to be careful online. Email is a wonderful thing, but it’s insecure. It’s a great way for criminals to get into our space and wreck havoc on our computers and our lives.
 

Read More