I'm running an Apache2 webserver on Ubuntu 20.04.2 LTS. I noticed that my access.log has several lines that simply say combine on them, with no information about the request or anything else. There are other lines in the access.log that do not say combine, and do have information about the request.
Here is a sample from my access.log:
combine
combine
combine
45.129.136.74 - - [26/Aug/2021:00:17:23 -0400] "\x03" 400 0 "-" "-"
45.129.136.74 - - [26/Aug/2021:00:17:23 -0400] "\x03" 400 0 "-" "-"
combine
192.241.204.78 - - [26/Aug/2021:00:23:55 -0400] "GET / HTTP/1.1" 200 546 "-" "Mozilla/5.0 zgrab/0.x"
84.54.153.88 - - [26/Aug/2021:00:27:54 -0400] "GET / HTTP/1.1" 200 621 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/601.7.7 (KHTML, like Gecko) Version/9.1.2 Safari/601.7.7"
combine
combine
45.146.164.110 - - [26/Aug/2021:01:02:57 -0400] "POST /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:57 -0400] "POST /api/jsonws/invoke HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:57 -0400] "GET /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:57 -0400] "GET /?a=fetch&content=<php>die(@md5(HelloThinkCMF))</php> HTTP/1.1" 200 565 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /?XDEBUG_SESSION_START=phpstorm HTTP/1.1" 200 565 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /solr/admin/info/system?wt=json HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /wp-content/plugins/wp-file-manager/readme.txt HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /index.php?s=/Index/\\think\\app/invokefunction&function=call_user_func_array&vars[0]=md5&vars[1][]=HelloThinkPHP21 HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /console/ HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "POST /Autodiscover/Autodiscover.xml HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.146.164.110 - - [26/Aug/2021:01:02:58 -0400] "GET /_ignition/execute-solution HTTP/1.1" 404 438 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.108 Safari/537.36"
45.129.136.74 - - [26/Aug/2021:01:05:21 -0400] "\x03" 400 0 "-" "-"
205.185.126.200 - - [26/Aug/2021:01:12:58 -0400] "POST /boaform/admin/formLogin HTTP/1.1" 404 475 "http://40.121.65.70:80/admin/login.asp" "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:71.0) Gecko/20100101 Firefox/71.0"
185.189.182.234 - - [26/Aug/2021:01:32:22 -0400] "GET / HTTP/1.1" 400 0 "-" "-"
42.193.16.135 - - [26/Aug/2021:01:34:15 -0400] "GET / HTTP/1.1" 200 565 "-" "Mozilla/5.0 (Linux; Android 10; LIO-AN00 Build/HUAWEILIO-AN00; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/78.0.3904.62 XWEB/2692 MMWEBSDK/200901 Mobile Safari/537.36"
206.189.182.136 - - [26/Aug/2021:01:45:23 -0400] "GET /ab2g HTTP/1.1" 400 0 "-" "-"
206.189.182.136 - - [26/Aug/2021:01:45:23 -0400] "GET /ab2h HTTP/1.1" 400 0 "-" "-"
combine
combine
combine
combine
combine
My apache2.conf has these lines:
LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined
LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %O" common
LogFormat "%{Referer}i -> %U" referer
LogFormat "%{User-agent}i" agent
Also in one of my sites-enabled configuration files I have this line:
CustomLog ${APACHE_LOG_DIR}/access.log combine
What do the combine lines mean in the access log? Why on earth would I care to see them? And how can I prevent the lines from just saying combine and make them actually show some useful information?
