If you are seeing “Waiting for comet.yahoo.com” message in the lower left corner of the window, then your system is infected with the malware. You could have picked up this infection when installing new software. This deceptive method is called bundling.
“Suspicious Activity Detected” is a scam message that popping up in Safari browser. This malware displays pop-up message to mislead credulous users and make them to call their technical support. There are highly trained people will contact you to impose unnecessary paid services.
Rambler.ru is in itself a legitimate search engine which has no relevance to browser hijackers. However, malefactors use it for their own gain creating malware that uses Rambler.ru search engine. Once infiltrated, malware replace your default search engine with http://www.rambler.ru page.
Search.watchtvnow.co might become your default search engine without your consent. That is because Search.watchtvnow.co is a browser hijacker that can secretly infiltrate the system. At first sight, there is nothing suspicious, but using this search engine puts the system at risk.
Optibuy is a typical adware that can crawl into system without your consent. Once installed, it starts to generate a bunch of ads (banners, coupons, pop-ups, audio and video ads, etc.) that will flood every page that you visit. This behavior really reduces browsing experience.