Category Archives: Security

The latest on handling of SHA-1 certificates by the major browsers

Posted on February 16, 2017 by john | 190 views

Intro A certain organization is still using SHA-1 certificates internally, in spite of years of warnings, as I write this in February, 2017. But in the security world lack of action = eventual weakness. Ignorance is not bliss and putting … Continue reading →

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The IT Detective agency: the case of the incompatible sftp client

Posted on December 1, 2016 by john | 449 views

Intro I was asked for assistance with this sftp problem: $ sftp <user@host> DH_GEX group out of range: 1536 !< 1024 !< 8192 Couldn’t read packet: Connection reset by peerDH_GEX group out of range: 1536 !< 1024 !< 8192 Couldn’t … Continue reading →

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drjohnstechtalk now uses HTTP Strict Transport Security, HSTS

Posted on November 22, 2016 by john | 159 views

Intro I was reading about a kind of amazingly thorough exploit which could be done using a Raspberry Pi zero. Physical access is required, but the scope of what this guy has figured out and put together is really amazing. … Continue reading →

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Roll your own dynamic DNS update service

Posted on October 13, 2016 by john | 801 views

Intro I know my old Cisco router only has built-in support for two dynamic DNS services, dyndns.org and TZO.com. Nowadays you have to pay for those, if even they work (the web site domain names seem to have changed, but … Continue reading →

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Internet Explorer can’t access https page – maybe a client CERT is needed?

Posted on July 22, 2016 by john | 238 views

Intro I don’t see such issues often, but today two came to my attention. Both are quasi-government sites. Here’s an example of what you see when testing with your browser if it’s Internet Explorer: The details Just for the fun … Continue reading →

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IP address wall of shame

Posted on July 12, 2016 by john | 270 views

Intro It can be very time-consuming to report bad actors on the Internet. The results are unpredictable and I suppose in some cases the situation could be worsened. Out of general frustration, I’ve decided to publicly list the worst offenders. … Continue reading →

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Idea for free web server certificates: Let’s Encrypt

Posted on June 13, 2016 by john | 199 views

Intro I’ve written various articles about SSL. I just came across a way to get your certificates for free, letsencrypt.org. But their thing is to automate certificate management. I think you have to set up the whole automated certificate management … Continue reading →

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Microsoft Exchange Online Protection is not PCI compliant

Posted on April 12, 2016 by john | 487 views

Intro Microsoft’s cloud offering, Office 365, is pretty good for enterprises. It’s clear a lot of thought has been put into it, especially the security model. But it isn’t perfect and one area where it surprisingly falls short is compliance … Continue reading →

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The IT Detective Agency: Cisco Jabber stopped working for some using WAN connections

Posted on December 4, 2015 by john | 541 views

Intro This is probably the hardest case I’ve ever encountered. It’s so complicated many people needed to get involved to contribute to the solution. Initial symptoms It’s not easy to describe the problem while providing appropriate obfuscation. Over the course … Continue reading →

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The IT Detective Agency: WordPress login failure leads to discovery of ssh brute force attack

Posted on October 29, 2015 by john | 178 views

Intro Yes my WordPress instance never gave any problems for years. Then one day my usual username/password wouldn’t log me in! One thing led to another until I realized I was under an ssh brute force attack from Hong Kong. … Continue reading →

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