Scouts are only dangerous when the owner is playing.
Scouts are small devices that can be dropped in a sector. They notify their owners everytime a non-ally passes through that sector (via an in-game message stating sector number, trader name and timestamp).
Hunters will often put scouts in sectors with ports (good ones anyway), so you're unlikely to find a proper trade route without triggering any scouts. But since only the scout owner (and not his alliance) will get the message,
you're safe as long as you are certain the player is offline.
Mind you, though, the scout owner
will be notified when he logs in, albeit with outdated information. Even though you may not be there anymore when he sees the message, he may come looking for you at another time, so don't feel too comfortable.
Morale: trade across scouted sectors if you must, but be wary of any scouts in your lanes and
check the Current Player List (CPL) regularly to see if any hunters could be on the prowl.