Q:

My server is under DDoS. What does this log mean?

Earlier today I got an email from my hosting provider that my server is being DDoSed. I found in log file many suspicious requests with some random site names like dekhockeyvicto.com, workout.de and very strange dish_fiber.dedicated:
13/Sep/2017:10:35:21 +0300] "GET http://dish_fiber.dedicated/alogin?dst=http%3A%2F%2Fviewdns.info%2Freverseip%2F%3Fhost%3Ddekhockeyvicto.com%26amp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bt%3D1 HTTP/1.1" 400 0 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36"
52.119.20.4 - - [13/Sep/2017:10:56:46 +0300] "GET http://dish_fiber.dedicated/alogin?dst=http%3A%2F%2Fviewdns.info%2Freverseip%2F%3Fhost%3Dworkout.de%26amp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bamp%3Bt%3D1 HTTP/1.1" 400 0 "-" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/43.0.2357.130 Safari/537.36"

What is it? Is it DNS flood type DDoS atack or what?
Please help.

A:

welcome to the internet.
Someone is trying to use your server as a proxy to attack someone else's machine. It doesn't look like a DOS attack on your server. 
Since the attempts have been frequent enough to wake up the people you are paying to provide you with this support it rather implies the attackers are having some success. However your server seems to be correctly responding with a 400 response rejecting the request.
As long as you haven't some something silly like using a custom error handler which returns a large amount of content, there's nothing you can do about this. That's not strictly true - but from your question I get hte impression that you do not have the skills, budget and hosting to tackle the problem. 

