Normally, firewalls at cellular carriers are your best friends, screening out malware before it ever touches your phone. University of Michigan computer science researchers have found that those first lines of defense could be your enemy through a new exploit. As long as a small piece of malware sits on a device, that handset can infer TCP data packet sequence numbers coming from the firewall and hijack a phone's internet traffic with phishing sites, fake messages or other rogue code. The trick works on at least 48 carriers
