"Ball Hawk" is not an official attribute or ability in Madden NFL 15. It's community slang for a defensive back with elite interception skills.
The following ratings create a "ball hawk":
Archetypes to Target: Free Safeties (FS) and Ball-Hawk Cornerbacks (CB) with 90+ INT/PRC. Legends like Ed Reed, Deion Sanders, or created players with "Ball Hawk" specialist perk (in later Madden titles) exemplify this.