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Cake day: August 2nd, 2023

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  • An alternative definition: a real-time system is a system where the correctness of the computation depends on a deadline. For example, if I have a drone checking “with my current location + velocity will I crash into the wall in 5 seconds?”, the answer will be worthless if the system responds 10 seconds later.

    A real-time kernel is an operating system that makes it easier to build such systems. The main difference is that they offer lower latency than a usual OS for your one critical program. The OS will try to give that program as much priority as it wants (to the detriment of everything else) and immediately handle all signals ASAP (instead of coalescing/combining them to reduce overhead)

    Linux has real-time priority scheduling as an optional feature. Lowering latency does not always result in reduced overhead or higher throughout. This allows system builders to design RT systems (such as audio processing systems, robots, drones, etc) to utilize these features without annoying the hell out of everyone else.










  • Pretty sure expiry is handled by the local crowdsec daemon, so it should automatically revoke rules once a set time is reached.

    At least that’s the case with the iptables and nginx bouncers (4 hour ban for probing). I would assume that it’s the same for the cloudflare one.

    Alternatively, maybe look into running two bouncers (1 local, 1 CF)? The CF one filters out most bot traffic, and if some still get through then you block them locally?


  • I’ve recently moved from fail2ban to crowdsec. It’s nice and modular and seems to fit your use case: set up a http 404/rate-limit filter and a cloudflare bouncer to ban the IP address at the cloudflare level (instead of IPtables). Though I’m not sure if the cloudflare tunnel would complicate things.

    Another good thing about it is it has a crowd sourced IP reputation list. Too many blocks from other users = preemptive ban.


  • According to this post, the person involved exposed a different name at one point.

    https://boehs.org/node/everything-i-know-about-the-xz-backdoor

    Cheong is not a Pingyin name. It uses Romanization instead. Assuming that this isn’t a false trail (unlikely, why would you expose a fake name once instead of using it all the time?) that cuts out China (Mainland) and Singapore which use the Pingyin system. Or somebody has a time machine and grabbed this guy before 1956.

    Likely sources of the name would be a country/Chinese administrative zone that uses Chinese and Romanization. Which gives us Taiwan, Macau, or Hong Kong, all of which are in GMT+8. Note that two of these are technically under PRC control.

    Realistically I feel this is just a rogue attacker instead of a nation state. The probability of China 1. Hiring someone from these specific regions 2. Exposing a non-pinying full name once on purpose is extremely low. Why bother with this when you have plenty of graduates from Tsinghua in Beijing? Especially after so many people desperate for jobs after COVID.