Trade security with performance

The recent CPU flaw caused quite a mess. Most recent linux kernels have the problems patched, but what if I am willing to trade security for performance? I’ll need to compile my own kernel and here is how to do that on Ubuntu 17.

First, we need to make oldconfig. Basically copy the kernel compile config from Ubuntu and decide whether new features should be enabled

Here I…

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Why the hack?

Why attacking and hacking – proof of concept – causes service interruption – utilize compromised systems to attack other targets – steal compute power – build zombie network – ransome – attention seeking – personal reasons How does it happen – Webhack exploiting vulnerable apps or scripts – SQL injection – Overflow boundaries – Brutish password hack – Social hacking – Affected by compromised neighbors particularly in muti-tenant environments –…

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Meltdown and Spectre CVE-2017-5715

Numerous posts and announcements have been made available in past 48 hours[1]. I don’t want to embarrass myself trying to describe what they’re about. Here I want to measure the performance penalty for the kernel patch. Kernel update has been made available on CentOS 7 (3.10.0-693.11.6.el7), roughly 12 hours behind Redhat. Here is a quick test of mysql sysbench on a small instance on aliyun, AWS, and Azure. No impact…

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Using list and lookup in terraform HCL

Terraform delivers consistent build and save a lot of time from clicking and scrolling. But when the resources, in this case ec2 resources are slightly different, it may be necessary to create a tf config for every instance. That defeats the purpose of automation. By storing the differences in a list and use the lookup function to extract the values, I’m able to write the following tf config with little…

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Switched to aliyun international today. It’s incredibly fast compared to DigitalOcean in the same region. Monthly charge is reduced by almost 50% [1] Blazing fast Compared to what I previous used, network performance exceeds my expectation. My DO vm was in the same region. Very often I had to wait 3-10 seconds for my blog to load. After moving to aliyun, the site loads in under a second. Sorry but…

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Writing a wordpress plugin to filter comments

I’m completely new to wordpress plugin development. I want to write a plugin to delete comments I don’t want based on a keyword list. Update: WordPress already comes with this feature under Comment Moderation The code The code isn’t complex. It first use the preprocess_comment hook to check the comment content. If it contains hyperlinks, a 404 error will be returned and the comment will not be inserted into database.…

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