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Some organisations put their intranets behind firewalls that block access to almost all services. It is not uncommon to see only the HTTP and HTTPS ports open for free access.
However, there are many other Internet services that star programmers need in order to be productive. Among them are:
Internet Relay Chat and other forms of Instant Messaging. This allows star programmers to discuss problems and share solutions interactively with their peers, or just to take a break from work and chat.
SSH - Secure Shell - allows access to remote computers over the network.
BitTorrent - allows downloading some content that is otherwise not available on the Web, or that its download can be resumed faster.
rsync - allows for faster incremental downloading and mirroring.
And naturally, malware can easily propagate and survive using HTTP and HTTPS alone, and there are ways that clueful workers can overcome such restrictions.
At one of my workplaces, I was able to chat on the IRC, connect using IM, ssh to everywhere I wanted, etc. without any restriction. It was a liberating feeling and I felt at home there. At a more recent one, I needed to connect to a remote host, and invoke port forwarding in order to talk on the IRC which was annoying and error prone.
So make sure your firewall is not over-zealous and does not prevent legitimate uses.