I am Stumped. one laptop slowing down entire network

Just had the Tech out here and we looked at the orbi logs and its getting DDOS attacks every time i connect that computer and thats whats slowing down the network. but im not sure how or why its happening. super stumped. all i did was put an SSD in, restore the laptop, installed dropbox, itunes, icloud and some other stuff for my wife to do her college work with. i havent even browsed the web other than speedtest.net i did however remove the mcaffee that comes on it.. (bloatware in my opinion) and we traced the IPs from the attacks and they are from facebook and dropbox... im so confused as to what to do now lol