Adware accounted for the most malware infections in the first quarter of 2008, according to security vendor Panda Security.

The company's PandaLabs research group said on Tuesday that adware comprised 28.58% of the malware infections recorded during the quarter, followed by software Trojan programs, which comprised 25.46% of malware infections.

Trojan programs, however, represented 62.16% of malware samples. Luis Corrons, technical director of PandaLabs, attributes the prevalence of Trojan programs to efforts by cybercriminals to overwhelm the defenses mustered by computer security companies.

Zango, which makes adware that Panda calls malware, has in the past defended its software as offering valuable content and maintains that adware keeps Internet content free.

Panda presented its findings in its first quarter 2008 security report, which also predicts a rise in mobile phone viruses.

"Mobile phone viruses have been a looming threat for years," the report says. "In Q1 we must highlight the SymbOS/Beselo and WinCE/InfoJack.A, but more importantly the appearance of the first iPhone Trojan. The release of Apple's SDK will probably cause the appearance of more sophisticated iPhone attacks and infections, or even 'iMalware'."

At the same time, Panda's report notes that Symbian's mobile operating system remains the most popular mobile OS in the world and that popularity is what is attracting malware. According to Panda, 90.34% of mobile malware targets the Symbian platform, 4.14% targets Windows Mobile, 3.35% targets Palm OS, and 2.07% targets J2ME.

"The truth is, Symbian is still the top platform in the global market and therefore the most attractive to mobile phone malware creators," the report says.

Given that there's but a single known iPhone Trojan, it's tempting to dismiss the idea of iMalware as iFearmongering. But check back after the sale of 10 or 20 million iPhones and Panda may well have the last laugh. Where there's a mass market, cybercriminals are sure to follow.