Choosing the appropriate time and tool
Black Hats will pick the busiest times to hit your network and do it as slowly and quietly as possible. They will try to stay under the noise of normal operation. Yes, there are more eyes on the network at that time, but a smart cracker knows that if they are slow and quiet, heavy traffic is a good cover. If you have good intel on the workflows and staffing of the target company, you might choose to attack at a sparsely staffed moment, such as weekends or holidays. This often works better at smaller companies.
If you're the Security Operations guy and you're testing your own network, this is not a good idea. Test during your off hours – it's best when the CEO is asleep. If any accidents happen during the test, things can be fixed and running properly before the next day when the CEO is awake. Exploitation doesn't normally kill a system beyond repair during testing, but some exploits will sometimes hang a service or completely hang the system to the...