Millions of everyday consumer devices, especially knockoffs that you buy online, are being infected by a malware known as residential proxy software. This gives anyone – including hackers – a backdoor into home networks. The Digital Citizens Alliance estimates that there are 20 million of these back doors in the U.S. WSJ’s Jack Gillum test a few of these malware-riddled products to investigate how criminals are tapping into them to carry out cyberattacks and other types of illegal activity