Company and insider buying falls to the lowest levels in years this month

The falling level of share buying by insider executives and companies is a negative signal for the market, according to research firm TrimTabs.

"The best-informed market participants seem unenthusiastic about U.S. stocks at current prices," TrimTabs CEO David Santschi wrote in a note Tuesday.

"Insider buying is running at the slowest pace for October in the past five years."