The hacktivist group claimed the attack was in retaliation for a U.S. strike on a Tehran school that killed more than 175 people, most of them children.

Amid a paralyzing breach of medical tech firm Stryker, the group has come to represent Iran's use of “hacktivism” as cover for chaotic, retaliatory state-sponsored cyberattacks.

The logo of Handala, a pro-Palestinian hacking group also behind an attack on the Academy of the Hebrew Language on Wedneday, reportedly appeared on login pages.

What message did Handala put along with its logo in crushing cyberattack became a key question after Iranian-linked hackers wiped devices at Stryker. Employees logging into laptops and phones saw a ...