TCP is a stateful protocol. Per-connection state uses memory, so creating more connections will exhaust memory OR it will cause no more connections to be created - both cases are a form of DoS.
A naive approach is to initiate a lot of connections, but never complete the setup. That's a SYN flood. Another approach is to actually complete the handshake, then initiate a tear down and never complete it. The OS at the server end gets stuck with a lot of half-closed connections that may take many minutes to timeout and there's no application control over this. There's no control over this 'stuck' connections at the OS level either, the only option is to wait for them to die off as per TCP spec.
There are other variations, but you get the idea. I do agree though that these two guys are simply whoring for attention.
Don't forget to stuff the kernel buffers with a few (or many) megabytes of data before getting those connections 'stuck'.
The amount of time it will take for them to die off (as per the TCP spec) is 'infinity' since there is no provision in the protocol itself for detecting unresponsive peers. If your operating system implements a hack called 'tcp keepalive' then those connections will die in a couple of hours in a typical configuration.
TCP is a stateful protocol. Per-connection state uses memory, so creating more connections will exhaust memory OR it will cause no more connections to be created - both cases are a form of DoS.
A naive approach is to initiate a lot of connections, but never complete the setup. That's a SYN flood. Another approach is to actually complete the handshake, then initiate a tear down and never complete it. The OS at the server end gets stuck with a lot of half-closed connections that may take many minutes to timeout and there's no application control over this. There's no control over this 'stuck' connections at the OS level either, the only option is to wait for them to die off as per TCP spec.
There are other variations, but you get the idea. I do agree though that these two guys are simply whoring for attention.