According to the anti-malware and spyware specialist - which globally pools data from its CounterSpy and Vipre security software - the Zbot trojan accounted for 8.48% all global malware threats in October, a month-on-month increase of more than 25% on the figures for September.
Michael St. Neitzel, Sunbelt's vice president of threat research, said the threat posed by the Zbot trojan shows no sign of abating due to its effective versatility in stealing cached passwords, login credentials and data in certificates and cookies.
"The presence of six trojan detections in the top 10 indicates that trojans and social engineering from spam email and social networking sites continue to be popular tactics in malware creation", he said.
Interestingly, the biggest move on the list was made by BehavesLike.Win32.Malware, a heuristic detection for software that exhibits behaviours that Sunbelt said are typically associated with malicious threats.
Incidences of this malware variant, Sunbelt said, more than doubled month on month from 1.55 to 3.86%.
There were also seven new malware entrants to the top 10 in October - which Sunbelt said is typically a key time for new threats to emerge - including Trojan.ASF.Wimad, taking number four on the list with 3.35%; INF.Autorun at number five with 2.24%; and Trojan.Win32.FakeXPA (v) at number six with 2.18%.