To limit the amount of connections per IP address, you could do the following:
- Go to... Menu -> Limits -> Max Connections from Single Address -> and put the max number of connections you would allow per IP.
Or - Since they are using a download manager set to connect multiple times to get many pieces of the same file they are downloading, you could do the following:
- Go to... Menu -> Limits -> Max simultaneous downloads from single address -> and set it to 1 or 2. I use this method and it takes care of download managers quite nicely.