Sniffers

Packet analyzer (aka network analyzer, protocol analyzer or sniffer), computer software or hardware that can intercept and log traffic passing over a digital network
According to a new study, your browsing history may be even less safe than the last time you heard about how your browsing history is not safe. Researchers at the University of California trolled through a wide range of popular websites to determine which ones were collecting information ("history sniffing" or "history hijacking")