ABS light and RRRRRR noise

[Treb]

Help! My ABS light came on and now the truck is making a RRRRRRRRRR noise that sounds like a lawnmower. When I look under the hood, it seems to be coming from a little silver pump of some sort on the firewall just in front of the driver. Has 6 metal lines going in / coming out of it. Turn the key off, keeps RRRRRRR pumping. Had to unplug the connectors going to it to make it go off. Is the truck safe to drive? What does this little pump do? Never noticed it before it went bad! It's a 2003 2500 4WD. Is this the ABS pump? Posted this on 911 also but thought maybe more 3rd genners would be reading this board.

 

[Hoefler]

Anti Lock brake pump. Get it serviced ASAP!!