Where are the third-party domains in the webserver's access.log?

Question

linux

ISPmanager5 has strange entries in the webserver's access.log. Apache2+Nginx
Where did third-party domains come from? Zaprsy go not to the default domain.

81.4.102.172 - - [18/Aug/2017:09:10:07 +0300] "GET / HTTP/1.0" 200 14792 "www.simplanudas.com" "Mozilla/5.0 (X11; FreeBSD i386) AppleWebKit/535.2 (KHTML, like Gecko) Chrome/15.0.874.121 Safari/535.2"
86.124.80.238 - - [18/Aug/2017:09:10:07 +0300] "GET / HTTP/1.0" 200 14792 "glamourholas.com" "Opera/9.80 (Android; Opera Mini/7.6/35.4131; U; en) Presto/2.8 Version/11.10"
37.235.56.141 - - [18/Aug/2017:09:10:07 +0300] "GET / HTTP/1.0" 200 14792 "saxprivatas.com" "Mozilla/5.0 (X11; CrOS x86_64 8172.45.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.64 Safari/537.36"
81.4.102.172 - - [18/Aug/2017:09:10:07 +0300] "GET / HTTP/1.0" 200 14792 "www.xartpussy.com" "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/47.0.2526.111 Safari/537.36"
81.4.102.172 - - [18/Aug/2017:09:10:08 +0300] "GET / HTTP/1.0" 200 14792 "www.fraaonas.com" "Opera/9.80 (Android; Opera Mini/7.5/32.749; U; en) Presto/2.8 Version/11.10"
37.235.56.141 - - [18/Aug/2017:09:10:08 +0300] "GET / HTTP/1.0" 200 14792 "vintagapornxxx.nat" "NetFront 3.3"

Answer 1

I think this is referral spam .