Shadow

Shadow is a defensive alarm program that works In concert with other detection programs. It attaches itself to the Netrunner on a successful attack (vs. cyberdeck datawall), and then has to removed with a Killer (or something similar). While attached, any evasion program used from that point on has its strength reduced by the current STR of the Shadow. If this strength is reduced to zero or less, the program is useless.

Source

• Chromebook Volume 3, pg.77