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In March of 2015, the FBI took control of a Tor onion childporn website ("PlayPen"), then used an 0day exploit to upload malware to visitors's computers, to identify them. There is some controversy over the warrant they used, and government mass hacking in general. However, much of the discussion misses some technical details, which I thought I'd discuss here.
IP address
retrieving IP addresses is clearly a search
He is wrong, at least, in the general case. Uploading malware to gather other things (hostname, username, MAC address) is clearly a search. But discovering the IP address is a different thing.
Today's homes contain many devices behind a single router. The home has only one public IP address, that of the router. All the other devices have local IP addresses. The router then does network address translation (NAT) in order to convert outgoing traffic to all use the public IP address.
The FBI sought the
public IP address of the NAT/router, not the
local IP address of the perp's computer. The malware ("NIT") didn't search the computer for the IP address. Instead the NIT generated network traffic, destined to the FBI's computers.
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