Experimental probing, drilling for holes in security. Exploiting any security holes - acting like they are an insider, demonstrating that they have the ability to read, write and execute. The bragging phase. The hacker frequently is looking to discredit and embarrass. Hackers tend to use brute force.
Attacks are random and undirected.
Hackers will spend an inordinate amount of time trying to crack a system. Exploiting known system vulnerabilities. Exploiting know protocol vulnerabilities. Examining sources for new vulnerabilities. Spoofing IP source addresses.