At NYSE, no breach but "Hack" is back

A day after technical troubles hit the New York Stock Exchange, United Airlines and the Wall Street Journal, the word "hack" was in full view on the NYSE, starting with the opening bell.

"When you have computer glitches the same day involving three high-profile companies -- the NYSE, United Airlines (UAL) and the Wall Street Journal -- and then the next day people have 'HACK' baseball caps walking all over the floor, it's an interesting coincidence," Art Hogan, chief market strategist at Wunderlich Securities, said.

The veteran Wall Street strategist was referring to the daily tradition of a company on hand for the kickoff of trade, which on Thursday happened to be those employed with an Exchange-Traded Fund, or ETF, which in this case involved one that tracks the performance of a group of cyber-security companies and has the ticker HACK.

"It's human nature to let one's imagination get carried away and assume there was some kind of cyber threat, which manifested in the FireEye (FEYE) and Palo Alto Networks (PANW) of the world all going higher, so it's a particular and odd coincidence that the next day that the company sounding the opening bell" is an ETF dubbed HACK, Hogan said.

"It's pure coincidence, those are scheduled well in advance," JJ Kinahan, chief strategist at TD Ameritrade, said. "Maybe it's a bad coincidence, but still a coincidence."

"Yesterday's closure for several hours at the New York Stock Exchange was a little peculiar, and left plenty of room for conspiracy theories to come up," Mark Luschini, chief investment strategist at Janney Montgomery Scott, said.

The New York Stock Exchange has said a technical problem was to blame for Wednesday's malfunction, not a cyber breach or hack.