While neither CBK nor AIO3 use the term “screening router,” they both discuss how the packet filtering capabilities of a router can be used to block traffic much like a packet filtering firewall. Krutz and Vine use this term on p. 90.
“A scanning router” is incorrect. This is a nonsense term to distract you. “A shielding router” is incorrect. This is a nonsense term to distract you. “A sniffing router” is incorrect. This is a nonsense term to distract you.
References: CBK, p. 433 AIO3, pp.484 -485