What's this component?
It's a transient absorber / suppressor.

The 4 diodes form a full wave bridge feeding voltage spikes from D+ and D- to the 3V3 power rails plus it has a zener diode acting as a voltage clamp  across the rails to absorb any energy which causes the rail voltage to rise. 



A look at NXP Semiconductors application note AAAAn10753 which Nick Alexeev provided the link to show that one part which matches that functionality exactly is NXP's PRTR5V0U2F/K Ultra low capacitance double rail-to-rail ESD protector Datasheet here. This is effectively an Application Note for USB2 ESD protection and the impact of protection on the USB signals - worth reading.