what is insidious:
As insidious qualify are what look like harmless or benign, in spite of hidden potential damage. The word, as such, is an adjective that is derived from the latin insidiōsus.
In this sense, insidious may be that person who is kindly and wicked, even naive, however, weapon snares, weaves delusions and hides perverse thoughts. From there that someone insidious is treacherous, disloyal, vile and unworthy of trust.
Insidious may also refer to the conduct or form of acting that hidden evil purpose, in spite of disguise themselves as harmless, benign appearance. In this sense, an insidious behavior is synonymous with malicious, misleading, or perverse.
Insidious in medicine
In medicine, as insidious qualify to all that illness or disease which, despite having benign appearance, hides great gravity. In this sense, insidious diseases may begin gradually or slowly, without too significant at the beginning symptoms, so if you have it is not fully aware of its severity.
In law such as insidious procedure is called one who relies on media that hiding or concealing the criminal intent. A classic example is the murder by poisoning, poison can be supplied with a food or beverage. The insidious procedure is, of itself, insidious and, in this sense, an aggravating circumstance of the criminal responsibility.