While the act of placing a mark is an illegal activity, the act of simply having a mark is not. Once you have the mark, you are considered a legitimate user.
Based on that line, I don't think spotting a mark will throw up any warning flags. Even if the Patrol IC saw your mark it wouldn't register it as odd.
What I'd like to do is define a reasonable pattern of behavior for Patrol IC that is not too time-consuming or difficult for the hacker as well.
How does this sound?
1. Patrol IC automatically examines all "loud" icons every turn. If you are a loud icon and do not have a mark on the host, then you are unauthorized and it triggers the alert. (I don't know if this is a valid scenario- is there a way to enter a host without having at least one mark?)
For a decker I don't think this is possible; I'm wondering if a Technomancer could achieve this with the use of Puppeteer or Resonance Veil, but I somehow doubt it.
2. Patrol IC will scan for silent icons "periodically". That depends on host configuration, security level, "alert status" of the host. For example, if another hacker just broke into the system and was caught, Patrol IC would constantly scan for silent icons which might catch me even though I haven't done anything yet.
I think this is fair. Scan every icon on entry, and periodically scan if an active alert is issued (i.e. failed sleaze or successful attack). In the case of a failed sleaze, though, the host gets a mark on you anyway, so in theory your cover is already blown as anyone can automatically spot an icon they have marked. That being said, a clever and fast hacker could potentially have time to erase the mark and hide before the IC got a chance to look for the offender, so it makes sense that Patrol IC actively look for hidden icons when an alert is issued.
3. If the Patrol IC spots a silent running icon, it will check if they have a mark. If they have a mark they will ignore them, but they're still spotted so an illegal action would automatically be detected. (You could change this so that any silent running icons are always illegal and immediately trigger an alert but that feels a little harsh).
I like this, though this is somewhat like 1 in that it's seems difficult, if not impossible, to enter the host without a mark in the first place.
4. Whenever an illegal action is committed, the Patrol IC does a Matrix Perception test to detect the aggressor. Spotting will result in an alert. Even not spotting could result in increased "alert status", see #2 above, depending on the host.
That's a little too much in my opinion.
5. Whenever some other custom-defined action is taken, the Patrol IC does a Matrix Perception test as above in #4. This is configured by the host. For example, if there's a super special file that only the owner should be able to edit, that would count as an "illegal action" and trigger #4's test. Note that a host -defined illegal action does not increase overwatch score.
How does that sound? Is it too harsh, or too easy?
This is more reasonable to me. You could even have honeypot files set up to always trigger an alert if modified in any way (heh), but a custom response certainly should keep players on their toes as long as they have some way of finding out about potential traps. Good recon should pay off.
I'd probably run Patrol IC as checking the door, so to speak, looking for icons running silently which would trigger a mechanical roll when a decker attempted to silently enter the system at the very least. In order not to slow down the game too much I'd probably just make the Patrol IC check only after an active alert (i.e. a successful Attack action or failed Sleaze action) and then periodically once per combat turn after that. Feels like a solid compromise between risk of discovery and flow of play to my mind.
I honestly don't think any illegal actions should provoke a Matrix Perception Test since they already have downsides on success or failure.
I'm not sure I agree with this. Nearby guards get perception tests to hear the silenced gunshot that you just took, and astrally perceiving or projecting mages get a chance to spot spells you just cast whether the action was successful or not. The fact that an action has consequences should not preclude further consequences, necessarily.
I think Patrol IC should not care if you enter a host, silent or not. Because you have a mark so it means you're a "legal" user. And if you're silent then it shouldn't know you entered, since that's the point of running silent.
This comes down to system design in my opinion. If you have a corporate host where running silent is off limits, icons that are running silent should be something that Patrol IC looks for. Is it applicable to all hosts? No. But it should certainly be allowed for some where higher security is desired.
I also don't think Patrol IC should make perception tests on illegal actions, because illegal actions already come with downsides. If its a successful attack action, the Host knows to start looking for who just attacked it. If its an unsuccessful sleaze action then it marks the hacker and knows to start launching IC to deal with the hacker.
I agree with this in principle, but some illegal actions set off the equivalent of alarms. A successful Sleaze and a failed Attack should not cause Patrol IC to look for icons running silent because it wouldn't know. But a failed Sleaze is something a Host would already know about, and a successful Attack is very overt but the cause may not be known, so Patrol IC looking for a culprit at this point makes perfect sense to me.
But legal Matrix actions that are performed from silent running persona's is strange. And that is when the Patrol IC should try to find the hacker or report it as a false positive or glitch and ignore it. Legal actions done while not running silent should be recorded and leave a data trail that the hacker won't want, which is why they won't want to not run silent and make a legal Matrix action, or maybe they would because they don't care if the IC spots them and would rather have that +2 dice.
There needs to be some risk to being in a host, obviously or else the corp would never use them. But it can't be so risky that the host instantly starts launching more IC and alarms go off and the entire run goes to drek, or else the Matrix becomes too much of a liability and no one will want to play it.
This gets too complex too quickly for my taste, which is why I'd run Patrol as checking everything at the door (first line of defense) and periodically after an active alert (second line of the defense). GOD notifying the host that a breach is underway (Covergence, and last line of defense) is the extreme prejudice option.