OK lets see here:
Overview. A Mac is no more secure than a PC, in fact right now the argument can be made that a Mac is less secure than a PC because there is such a long term focus on Windows security that many of the solutions implemented have yet to be ported to Macs..
PCs do have certain intrinsic weaknesses that tie into the role Explorer has with regards to interfacing with the operating system, and those weaknesses are legion mind you, but again its kind of an oranges v apples thing. Macs are softer (imo) but there is less knowledge floating around regarding how to take advantage of their weaknesses, so PCs can be considered the lower hanging fruit.
Now. If Mac actually comes through with a PC-buster, eg a laptop or desktop for half the current price with twice the hardware value, then I think what we will see is an inversion of sorts, where browser-based OSX exploits become far more serious/pervasive... but even now, major zero day browser based exploits will often determine what browser / operating system youre running and then direct you to an appropriate malicious payload. Thats kinda new. It used to be that people would just make their hostile malware PC specific and say fuck it re: the 5% of apple boxes that it doesnt affect. That 5% (or whatever it currently is) is no longer being ignored.
So:
Can a hacker infect a mac? (not just the Steve Blow-Jobs answer please)
Yes, 100%. OSX is a BSD based UNIX variant that can be subverted. Fairly easily in truth, once the equivilent of "administrator" access is attained (root, we call it). And there are a lot of ways to get root on OSX if you understand how to audit code/binaries and are so inclined.
Can someone install a keylogger without my password?
Yes, 100%. Once you have root access to an OSX computer, you have the literal keys to the kingdom. Your keystrokes can be logged, screen captured, webcam enabled. If it can be done on a PC it can be done on a Mac, basically. But again; for every 1 person who knows how to actually do this to a Mac there are probably 10,000 who know how to do it to a PC.
Can they control my webcam?
See above.
Is Internet poker safer when playing on a mac?
Its safer, sure. But you have to look at it like this; someone pops your PC while putting together a botnet for spam and DDoS and sees you are a regular 2/4 NL player, for example. Cool, its showtime, because they earn something like $80 US a month on the average and now they can take a years salary off you in one session.
Now lets imagine they get access to your Mac. Again, same villains. They are roaming around putting together a botnet, and they get into your Mac. Again, same thing, they see you playing 2/4 NL holdem.
Im going to put myself in their shoes; I can find someone in a few hours through networking who can put together a OSX rootkit, throw them a months wages for their efforts, and then grift you for 3 hours for a small fortune.
Why wouldnt I do that?
So you see, there is a hurdle presented by running a non-standard OS but at the end of the day, the grey market has a contingency plan for that hurdle, and most others as well.
Does sharig a wireless connection with an unprotective PC user endanger me in any form or lower my safely level?
Good question.. if you were a government employee or working with highly sensitive data (financial, medical, so on), then the answer is unequivocally yes.
If you want to play on FTP or Stars while your roomates girlfriend installs 50,000 trojaned freeware games on his PC, youre safe. FTP, Stars, pretty much all the big sites encrypt traffic between their servers and the client application.
Those data streams are secure. To compromise the integrity of the encryption or otherwise hijack the data would require aa quantity of talent and effort that would almost certainly be better spent elsewhere, so you would likely be a poor candidate for a random assault based off a rogue PC on the same network.
Caveat: if you are running a poker client that does not encrypt traffic (FYI I dont know of one) then you may have a problem, and if your Mac is running applications that can be easily exploited by the PC, you may also have issues if the PC-hijacker cares enough to go for it.
You have to remember; 99.99999% of all infected computers are automated attacks. Botnets today contain literally hundreds of thousands of nodes. You dont get that many computers by scanning and trying to penetrate computers one at a time. So really when discussing pragmatic security, you have to differentiate between the average threat (automated scans) and exotic threat (people aggressively trying to compromise your computer).
One of the reasons Im glad this forum exists is because I think the latter becomes far more realistic for internet poker players, as the sums of money at risk are extremely tempting and can justify large amounts of effort.