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Tag: dns

Flush your DNS cache (again)

This time it appears that DNS for major websites, including the NY Times, has been compromised. Attackers put in DNS entries that redirected visitors to a malware site. The compromise has been fixed and the fake DNS entries corrected. However, people may still have the old data in their DNS caches and security experts are […]

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SPF Fail: too many DNS lookups

I’ve had a couple folks come to me recently for help troubleshooting SPF failures. The error messages said the SPF record was invalid, but by all checks it was valid. Eventually, we tracked the issue down to how many include files were in the SPF record. The SPF specification specifically limits the number of lookups […]

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The death of IP based reputation

Back in the dark ages of email delivery the only thing that really mattered to get your email into the inbox was having a good IP reputation. If your IP sent good mail most of the time, then that mail got into the inbox and all was well with the world. All that mattered was […]

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Weird mail problems today? Clear your DNS cache!

A number of sources are reporting this morning that there was a problem with some domains in the .com zone yesterday. These problems caused the DNS records of these domains to become corrupted. The records are now fixed. Some of the domains, however, had long TTLs. If a recursive resolver pulled the corrupted records, it […]

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DNS, SERVFAIL, firewalls and Microsoft

When you look up a host name, a mailserver or anything else there are three types of reply you can get. The way they’re described varies from tool to tool, but they’re most commonly referred to using the messages dig returns – NXDOMAIN, NOERROR and SERVFAIL. NXDOMAIN is the simplest – it means that there’s no […]

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Maybe the sky is only falling a little bit

There was quite a bit of breathless reporting last week about the DoS against Spamhaus and how it was large enough to break the Internet. As the postmortem has gone on, a few things are becoming clear. There was a lot of traffic, enough to swamp some major transit points. Most people, particularly in the […]

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Internet Storm Center on the Spamhaus DOS

The Internet Storm Center (ISC) has a blog post up discussing the DOS attack against Spamhaus. They do confirm they saw traffic approaching 300Gbps against Spamhaus. They also point out that most people probably never knew. The attack was significant, but not globally so despite the media reports to the contrary. When news of the […]

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More on the attack against Spamhaus and how you can help

While much of the attack against Spamhaus has been mitigated and their services and websites are currently up, the attack is still ongoing.  This is the biggest denial of service attack in history, with as much as 300 gigabits per second hitting Spamhaus servers and their upstream links. This traffic is so massive, that it’s […]

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Troubleshooting tools

There have been a number of comments on my post about Hotmail moving to SPF authentication having to do with troubleshooting authentication failures. I have been helping clients troubleshoot these issues, and am able to take on new clients to solve authentication problems. Contact me for more information. Of course, many of these issues can […]

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Collaboration key to fighting crime on the internet

The Pittsburg Post Gazette has a good article on the DNS Changer Working group and how it can serve as a model for future collaboration against cyber crime.

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  • AOL problems

    Lots of people are reporting ongoing (RTR:GE) messages from AOL today.  This indicates the AOL mail servers are having problems and can't accept mail. This has nothing to do with spam, filtering or malicious email. This is simply their servers aren't functioning as well as they should be and so AOL can't accept all the mail thrown at them. These types of blocks resolve themselves. 1 Comment


  • Fixing discussion lists to work with new Yahoo policy

    Al has some really good advice on how to fix discussion lists to work with the new Yahoo policy. One thing I would add is the suggestion to actually check dmarc records before assuming policy. This will not only mean you're not having to rewrite things that don't need to be rewritten, but it will also mean you won't be caught flat footed if (when?) other free mail providers start publishing p=reject.No Comments


  • Sendgrid's open letter to Gmail

    Paul Kincaid-Smith wrote an open letter to Gmail about their experiences with the Gmail FBL and how the data from Gmail helped Sendgrid find problem customers. I know a lot of folks are frustrated with Gmail not returning more than statistics, but there is a place for this type of feedback within a comprehensive compliance desk.No Comments


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