China gets horny
Today I woke up to several alerts from Linode informing me that one of my VPS nodes was exceeding the Disk I/O threshold that I had set. Curiously this VPS is used as a HTTP web proxy and whilst it gets about 300-400 visitors per day (mainly china) this morning I was seeing over 800 visitors in Google Analytics.
Attempting to ssh to the server failed with timeouts although the PHP web application was still responding to requests over HTTP fine. I suspect sshd was failing to reverse-lookup my IP address in any reasonable amount of time, or perhaps IP Tables – (Note to self: Look in to why that happened). Thankfully Linode provide out of band / console access via SSH and AJax so all was not lost.
Looking at the Network rrdgraph it shows that the server was approaching 7Mbit/s of HTTP traffic and almost 50GB had been consumed today alone. Whilst the server seemed to handle the load without problem (minus ssh access) consuming 50GB+ per day would quickly max out my monthly data transfer allowance with Linode – this wasn’t acceptable. I modified the firewall to accept HTTP/HTTPS traffic from my IP only in order to investigate and the load suddenly stopped and SSH was alive again.
Initially I had suspected that some sort of automated bot was using ehproxy.info to do automated scans and attacks but a closer inspection of the traffic showed an even number of distributed IPs (all from China – as Google Analytics confirms) all clicking various porn sites. I guess everyone in China was feeling horny this afternoon!
Further analysis of the access.log shows that the server (Linode XenU VPS with 720MB of ram) was handling 62 hits sec (2428863/39600) and lighttpd was dealing with the load no problem. Pretty good considering this is a pure PHP application utilising php-cgi.
For the record, the top five IP addresses were:
Hits : IP address
