How much does it cost to infect 1,000 machines with malware? Russian services will do it for as little as $12.

Distributed denial of service (DDoS) attacks, which overwhelm a website with traffic, can be purchased for as little as $10 for a 1-hour attack, Trend Micro says. A one-day attack costs $30 to $70.

A global mix of malware downloads, for example, costs as little as $12 per 1,000 downloads. U.S. downloads are slightly more expensive, priced at $100 to $150 per 1,000 downloads.

Make sure you have a firewall that can scan for these type of threats at the gateway. Also make sure that you are not running admin rights on your machine and you can prevent this.