In a tough environment, one's ability to scam others is not seldom a sign of industriousness, as illustrated by the saying "el que no transa, no avanza" (lit. one doesn't prosper without swindling).
Probably the expectation of most people being involved in some sort of scam gave rise to the expression ¡¿qué transa?! (lit. what's the scam?!), which means "what's up!", and its further transfiguration into ¡¿qué transita por tus venas?!* (lit. what flows through your veins?!), which retains the exact same meaning and is an exceptionally colorful greeting. This expression does not imply the greeted person is dishonest.
*Notice that transa is switched for transita (lit. little scam, also to transit) because they share the same phonetic root and are otherwise unrelated.