During April and May 2010, the number of Trojans in the total amount of malicious software delivered through e-mail accounted for 69%. Indeed, since 2010 beginning, the total amount of malicious software through e-mail per month has risen over four times, from 0.01 to 0.1%.

The security analysts from 'Eleven' stated that this demonstrates that the malware developers are giving the top priority to the botnet expansion, which has grown significantly in intensity.

In addition, according to the security company, there has been a return of the Sasfis Trojan in multiple versions that captured the first three spots amongst all malicious software disseminated via e-mail. TR/Crypt.ULPM.Gen, accounting for 40.77% of the total malicious e-mails, HIDDENEXT/CryptedHIDDENEXT/Worm.Gen and HIDDENEXT/Worm.Gen;HIDDENEXT/Crypted respectively.

These variants have a common characteristic, that is, they spread essentially posing as delivery e-mails supposedly from package delivery firms.

Besides the above discoveries, Eleven's study further indicates that a huge 87% of the total junk e-mails were based on pharmaceutical promotions like those of Viagra drugs. An interesting trend that the security company found during May 2010, however, was that junk e-mails were based on several topics like a single message promoting watches and pharmaceuticals.

Moreover, during April and May 2010, spam mails were distributed far more uniformly across different nations in contrast to the earlier months. This shows that botnet proliferation is reaching higher number of regions.

Also, spam dispatched through American Internet Protocol (IP) addresses was the highest among all geographic regions, contributing a share of 8.0%. German IP addresses dispatched spam a little less than the US IP addresses, accounting for 7.8% of the total e-mail junk. Finally, on 3rd and 4th places were India (at 7.3%) and Brazil (at 7.2%) respectively, the report disclosed.