For an internal breach it is very unlikely. the checks and balances you have in place for financials is absolutely ridiculous. Not to mention datacenter control. The greater threat is from an outside source like anon. You have to remember anon has some extremely brilliant minds. Some of those guys are just unreal. The thing with hacking is there will always be flaws and threats. You just have to find it. Those guys are very good. so good its scary. Sheena if you want I can sit down with you and chat about it but its a shit ton to type and im tired. lol. But once you get into an enterprise level environment its pretty crazy. If you knew all the audit stuff I have to deal with and the paperwork and BS you'd be amazed. I'm actually a system admin with a security focus. Im actually taking my cissp in august so most of this stuff is up my alley.
on the flipside. my environment is huge. think 1500 plus servers and 7500 workstations. It would not be hard for someone to slip through the cracks with info. In fact what I do daily would be a hackers dream to get their hands on as I'm responsible for threat and vulnerability management, risk assessment, and remediation for all that. who wants my job? lol. At least count there was almost 24000 hosts on my network.