When Marsh is describing how the killer penetrated her wireless network, she launches the "Horsez" game on her daughter's computer. The taskbar clearly belongs to Windows XP, but the window that pops up is styled like a Vista Aero window.
When Agent Marsh's car loses electricity, she is forced to break a window to exit the car. All cars can be unlocked from the inside without electricity.
When Agent Marsh is in the car listening to the radio it displays the frequency as 108.9FM. FM Radio dials only go to 107.9.
When Collin Hanks character does a look-up for "Blue Sky ISP" he types in 10.12.121.99, which is a Private IP or non-routable address. The search wouldn't return any information.
In the beginning of the film, Jennifer Marsh says that someone is registered with two firearms. There is no firearm registry in Oregon.
The FBI does not have immediate access to firearm ownership records. Agent Marsh would have to violate the law in order to gain the information in the manner portrayed in the movie.
Incorrectly regarded as a goof: the filming of the agent's body in acid shows the liquid full of blood but it is later clear - that would be correct; the acid would probably have bleached the blood so that it would have reverted to the 'straw' colour of blood plasma.
When the forum posts are being shown at the end of the movie, new posts show a time stamp of "> 1 minute" ago. It should be "<" for less than.
When Annie is playing the "Horsez" game, the button commands shown are for that of a Sony PlayStation, not a computer.
When Jennifer is hanging upside down, her hands were tied but not her arms, so she could remove the piece of fabric around her mouth and reveal her location.
When the daughter looks out the window upon seeing her house on the computer, the crew can be seen on the far right of the screen through the window next to the one she is using.
When Jennifer Marsh's electrical system is restored on her vehicle, she makes little effort to check the inside of the vehicle before re-entering it. A highly trained police officer, especially a FBI agent, would have enough sense to check the back seat throughly before making any attempt to re-enter a vehicle considered suspicious.