Ten years ago, Michael Riva was network administrator for a top-five American consultancy. Employees were downloading graphic pictures and videos onto the network. Riva told his boss a proxy server with content filtering might be in order; his boss laughed and suggested they put in a bigger file server instead.

Riva stood his ground and was gone a few weeks later.

Though some would look at this as a career mistake on his part, Riva would gladly do it again. What's right is right, he says.

After asking security professionals about some of the worst (publishable) mistakes they've ever made on the job, CSO decided to ask about mistakes professionals would gladly make again. Best mistakes, if you will, that ultimately paid off either personally or professionally.

Here are five such tales:

1. THE PORN DISCOVERY

Mistake maker: Michael Riva

Position: Network administrator, IT consultant

Location: Currently in Ireland

The incident: Bosses didn't like his idea of blocking porn

"Ten years ago I was working for one of the top-five American consultancy companies as a network administrator. At the time we had a file server with 40GB of disk space. This was pretty descent space, knowing that it was serving over 500 people. Over a short period of time, however, the disk space went to less than 500 MB. People had problems saving documents and so on.

"One day I decided to clean up a bit and implement disk quota with a third-party tool for the Windows NT 4 server. To my surprise, I noticed more [network space] being used by some consultants who saved a lot of pornographic content. There were all sorts of crazy things on there. I deleted the content without asking anything and a few days later the content was back. A few people were actually flooding the server with those videos.

"I spoke to the IT manager and suggested we implement a proxy server with content filtering. He laughed at me and told me we would buy a bigger file server instead. He also said the consultants are the fuel of the company; each one of them was bringing [US]$1,500 to the company every single day.

"After a few weeks I was gone because the senior partners heard about this and my quest to eradicate those files did not please them. I reckon that in such a situation nowadays the IT manager would have been let go instead. I was 22 years old at the time but was still shocked by the behavior."