We can choose to to filter categories by default (advertising, pornography) or set our own parameters and add exact URLs we don't want to be accessed from our computer.
The settings panel offers the possibility to set if you want to filter only TCP or UDP traffic or if you want to filter all IP protocols. Teh program keeps you informed about the internet activity and the websites that have been filtered.
SIFT is an interesting application, although it is in an early development stage and can present some stability problems. So it's recommendable to collaborate with the developers sending them bugs and feedback.