Pingdom AB.

List of most popular unknown user agents of Pingdom AB.

Useragent	Info
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/61.0.3163.100 Chrome/61.0.3163.100 Safari/537.36 PingdomPageSpeed/1.0 (pingbot/2.0; +http://www.pingdom.com/)
pingdom-bot
Pingdom.com_bot_version_1.4_(http://www.pingdom.com/)
Pingdom GIGRIB (http://www.pingdom.com)
Mozilla/5.0 (compatible; pingbot/2.0; +http://www.pingdom.com/)
Mozilla/5.0 (Unknown; Linux x86_64) AppleWebKit/534.34 (KHTML, like Gecko) PingdomTMS/0.8.5 Safari/534.34