The backlash against a formerly obscure California mobile-monitoring software maker grew even larger Thursday, with a senator asking questions, citizens bombing the company with bad online reviews, and former customer Apple swearing it off.

Adding possible legal jeopardy to its woes, a former federal prosecutor is also publicly wondering whether Carrier IQ, whose phone-monitoring software was secretly installed on millions of phones, was illegally wiretapping Americans’ communications.

Carrier IQ’s software is installed on phones sold by Sprint, T-Mobile and AT&T, among others, and is intended to help carriers know what problems users are having and what features are most popular.