What does the attacker want and is it dangerous?

Question

Nginx

The following entries began to fall into the nginx_access log:

[15/Apr/2014:16:25:56 +0400] "GET http://www.[MY_SITE_COM]/?a=tt4mq2&b=e33bu HTTP/1.1" 200 7238 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0"

[15/Apr/2014:16:25:56 +0400] "POST http://myinfo.any-request-allowed.com/?a=tt4mq2&b=e33bu HTTP/1.1" 301 178 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64; rv:28.0) Gecko/20100101 Firefox/28.0"

Tell me how to filter it and whether it is necessary?

Answer 1

[sarcasm]
This is A/B testing.
[/sarcasm]

Answer 2

Perhaps the server was / is part of the bot network. And these are commands. I will assume that the site has standard WP, ​​Joomla, or some other mass software. Statuses other than 404 hint that the engine did something to these requests and even responded.

Answer 3

On the nginx/nodejs server. And what these requests should lead to a 404 error? The first request simply requests the main page and gets a 200 OK response, the second gets a permanent redirect and that's it.
They just got tired of hanging out in the logs. What is the best way to get rid of them?