Bemused Toronto commuters were repeatedly informed that "Stephen Harper eats babies" after a hacker tampered with advertising signs on city trains.

The scrolling electronic signs that usually carry transit updates and advertisements on Toronto's westbound Lakeshore GO Transit trains carried the messages Thursday, Friday and Monday after the hacker used a remote-control device to re-program the wording and mock the prime minister.

The ingenious hacker made sure that suburban commuters in at least five different cars continued to get his or her subliminal message.

Commuter Gerry Nicholls said he thought he was hallucinating as he relaxed in his seat for the 35-minute GO train ride between Toronto and his Oakville home.

Every three seconds, the scrolling electronic sign read: "Stephen Harper Eats Babies. Stephen Harper Eats Babies. Stephen Harper Eats Babies," Nicholls told the Toronto Star.

"No one seemed to be reacting to it," said Nicholls, who happens to be vice-president of the National Citizens Coalition, the same conservative think-tank formerly headed by Prime Minister Stephen Harper.

"I kept waiting for the kicker,'' he said.  "I thought, there's got to be something to this. It's a joke,  it's an ad for baby food or something like that. It just kept going over and over again and I realized that this is something that could be pretty serious.

"I wasn't even sure when I got off the train. Was I hallucinating?"

The case of "electronic vandalism" prompted red-faced GO Transit officials to pledge the insults would never happen again.

To do so, they will have to power down all the signs on their cars and use special software that is being couriered from the United States to password protect the digital signs, a process that is expected to take three days. 

"Unfortunately it's a slur, it's an offensive message," GO Transit spokesperson Ed Shea told the Star.

"We regret it happened and we're sorry if anybody was offended, including the prime minister."

However, a digital security expert told The Globe and Mail this kind of digital tampering is as easy as buying a $23.95 gadget -- and more of it should be expected.

"There's actually a whole slew of ways to hack into these signs," said Ryan Purita, a forensic examiner with Totally Connected Security Ltd. in Vancouver.

"If people don't think those things are connected to the Internet, they're wrong," Purita told The Globe.

Dimitris Soudas, a spokesman for Prime Minister Stephen Harper, described the hacker's actions as "inappropriate and disrespectful."

Meanwhile, when asked about his time with Harper at the National Citizens Coalition, Nicholls said: "I worked with Stephen Harper for five years and never once did he, in that time, eat a baby."