Why do link shorteners open pop-up ads?

When using low-reputation URL shorteners to download files, it is common for multiple tabs of deceptive ads and fake Windows tech support alerts to open uncontrollably.

Blocking malicious URL shortener connections

These pages monetize through aggressive ad networks that host exploits. AdBlock Network neutralizes these connections. The software makes asynchronous, read-only requests to multiple independent endpoints to keep the local firewall updated, denying connections to spam servers at the Address layer.