The number of malware attacks against Android devices has exploded by 400 percent since the summer of 2010, according to a new study by an Internet security research firm.

The Juniper Networks Global Threat Center compiled the study, titled “The Malicious Mobile Threats Report 2010/2011,” and finds that smartphones are continuing to come under attack by criminals intent on committing identity theft.

Technolog has the story, which rounds up some key points from the study and notes that a large part of Android’s high number of attacks seems to be its popularity around the world. Analysts have projected that half of all smartphones will be using the operating system by this time next year. Before Google’s (GOOG) Android hit the scene, it was Nokia’s (NOK) Symbian operating system that was the victim of most attacks.

Juniper Networks (JNPR) pegs the problem with users failing to protect themselves when they use smartphones the way they might if they were using computers. This isn’t the first time that we’ve heard about smartphone users being oblivious to security concerns, with one recent survey stating that only about one in 10 smartphone owners employ some kind of security software.

According to the study, in addition to malware coming in apps that users download, text messages are also a big security hole: “17 percent of all reported infections were due to SMS trojans that sent SMS messages to premium rate numbers, often at irretrievable cost to the user or enterprise.”

Some other quick hits form the study: Juniper reports 1 in 20 of its customers lost devices or had them stolen, requiring the use of locate, lock or wipe commands to be used to save data from prying eyes; and 20 percent of teens say they have sent explicit or “inappropriate” content using a smartphone or mobile device.

There are some steps you can take to protect yourself when you use a smartphone, and Juniper recommends looking into antivirus software for mobile devices that can help protect it from malware and intrusion. The company also suggests making complex passwords that contain capital letters, symbols and numbers without full words — the kind of steps you’d take to protect passwords for use on computers — and using device-monitoring software on kids’ phones to make sure they’re not sending things over the air they shouldn’t be.