One in seven home networks in North America are infected with malware, a recent study has revealed.

Half the threats detected during Q3 2012 were made up of spam-spewing zombies or banking Trojans while the remainder were mostly adware and other lesser threats, according to a study by Kindsight Security Labs. The study was based on data gathered from the security firm's service provider customers.

Kindsight Security Labs offers Phorm-like deep packet inspection technology to consumers through its telco partners. Consumers get pushed behavioral advertising sweetened by the promise of malware screening. Kindsight therefore has a vested interest in talking up the malware threat so its figures need to be viewed with caution even though they present a interesting insight into the botnet landscape, which everyone agrees is pretty dire.

The one-in-seven (13 per cent) infection rate recorded by Kindsight in Q3 is actually a 1 percentage point improvement on figures recorded in Q2 2012.

Consumers most commonly get infected with malware after visiting websites contaminated with exploit kits via so-called drive-by attacks.

Kindsight names the ZeroAccess botnet as among the worst menaces to internet hygiene. ZeroAccess was the most active botnet in Q3, with more than 2 million infected users worldwide with 685,000 in the US alone.

"These bots are engaged in a sophisticated ad-click fraud scheme that each day generates about 140 million fraudulent ad-clicks and 260 terabytes of network traffic. ZeroAccess could be costing advertisers $900,000 per day," according to Kindsight.

The second most active botnet in Q3 2012 was TDSS/Alureon family, also known as TDL-4.

The security firm's Intrusion Detection System-based technology runs in the networks of both fixed line and mobile service providers, monitoring threats. This allows Kindsight to see attack traffic spewed out by infected handsets onto mobile networks.

The infection rate of Android smartphones is just over 3 per cent, according to Kindsight's statistics. Mobile adware accounts for nine in 10 of these cyber-undesireables, it adds. More serious Android nasties the study detected were almost exclusively “Trojanised” apps, which steal information from smartphones or send SMS messages to premium-rate numbers without the permission of owners.

Kindsight's full report can be found here (PDF). ®