Category Archives: Network Technologies

Network Technologies

Bluecoat ProxySG and DNS using edns seem incompatible

Intro Imagine your DNS server had this behaviour when queried using dig: $ dig drjohnstechtalk.com @146.201.145.30 ; <<>> DiG 9.9.2-P2 <<>> drjohnstechtalk.com @10.201.145.30 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: FORMERR, id: 48905 ;; flags: … Continue reading

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Use Raspberry Pi to explore mDNS

Intro I am confounded by the Bonjour field on my d-Link DCS-931L IP webcam. I should be able to use it to se my desired hostname, but it doesn’t take. Why? The details Having a Raspberry Pi on the same … Continue reading

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Switch home router to DD-WRT: FAIL

Intro I am having problems with my home router, a Cisco E1200, especially with the wireless connections. I thought it might be interesting to try to run it using the open source routing code DD-WRT. Since I am a Linux … Continue reading

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

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 peer We actually spoke with the operator of the sftp server … Continue reading

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drjohnstechtalk now uses HTTP Strict Transport Security, HSTS

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

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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Who’s using the UK Ministry of Defence’s IP addresses?

Intro When I first came upon a spear phishing email a few months ago which originated from the UK’s Ministry of Defence I thought that was pretty queer. Like, how ironic that an invoice scam is coming from a Defense … Continue reading

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

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

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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The IT Detective Agency: the case of the mysterious reset

Intro An F5 BigIP load balancer equipped with web application firewall worked for everyone, except one app used by one customer. What was going wrong? Packet trace I always do a packet trace when there is nothing else to go … Continue reading

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