Khalid Masood killed four people in Westminster this week. It is understood his phone had connected to messaging app WhatsApp two minutes earlier.
Amber Rudd said she would be meeting technology firms this week.
A WhatsApp spokeswoman said the company was "horrified at the attack" and was co-operating with the investigation.
Meanwhile, a 12th arrest has been made by officers investigating the attack. The 30-year-man was detained in Birmingham on Sunday on suspicion of preparing terrorist acts.