I have 8 cams total. 7 are hardwired and 1 wireless. I went with wired cams for 2 reasons. the first is that 3 of the wired cams are nightvision non X10 cams (IR cams) and wired gives better images and the second reason was range issues. The wireless cam looks out over the drive and is also a non X10 nightvision cam. The other cams are inside buildings, a stairwell, garage and kennels. I really haven't thought much about anyone intercepting the wireless cam but i guess they could. If they wanted to look at the cam looking at the driveway they would get a better picture if they just parked by the drive.
If the cams are inside looking out it wouldn't make any difference if they could see them or not. Sound could be an issue but that could be blocked as indicated earlier in this thread. By far wired cams give you the best image and most security against outsiders.
Also someone would have to know what you have and have portable equipment to park outside and try and pick up the signal. Guess I would wonder why someone would want to do that just to do it. If they are crooks staking you out then you must have something they want. If that's the case no security would be 100%. Locks, security systems and cameras keep honest people honest and detour amateur crooks. Professional crooks can beat almost any systems. My outside cams are all highly visible and I have a professional sign in the front yard says I'm protected by a security system. There have been a few houses in the area that have been broke into, one right across the street last year. No houses with signs have had breakins yet.
I just saw an article in the local paper about a hobby shop that was robbed. They broke into a rear door and disabled the alarm system. The second thing they took out was a camera system. They took around $50,000 of collectable train sets. So much for security
The police said the thieves were professionals.
All any of us can do is try and keep our own little part of the world safe and secure and share with others what seems to work for us.