ON APRIL 27, a mysterious Twitter user named @GreyManrod issued two cryptic messages. One read: “Nap time. Back in 60 Min.” The other: “@UCI_Overlord 60 Min took over for you on that project.”

The tweets might have seemed nonsensical—unless you knew that the person writing them was actually Floyd Landis, the 2006 Tour de France champion who had his title revoked after testing positive for synthetic testosterone. For the past few months, Landis, who is now retired from cycling, has been conducting what he describes as a “satirical” Twitter assault designed to antagonize and discredit Lance Armstrong, his old U.S. Postal teammate and current foe.

Landis, 35, sent the tweets after being contacted by CBS producers about an upcoming 60 Minutes interview with Tyler Hamilton, which aired May 22. Why? Landis believes Armstrong is engaged in his own campaign of online disinformation, and Landis hopes to expose Armstrong’s hypocrisy. “I’m out to demonstrate how few people understand how easy it is to manipulate perception using the Internet,” he told Outside in an e-mail. In particular, Landis believes Armstrong’s camp is engaged in a concerted effort to buoy the seven-time Tour de France winner’s image—which has been tainted by increasingly frequent doping allegations—by routinely posting prescripted pro-Lance comments beneath online stories about Armstrong, a claim Armstrong flatly denies.

That’s the high-minded explanation, anyway. Down on the low road, it’s obvious that @GreyManrod—a handle Landis says he shares with about ten other people—simply likes giving Armstrong a hard time. For example, after Armstrong’s recent run-in with Hamilton in an Aspen bistro, Manrod poured fuel on the fire, tweeting and retweeting rapid-fire insults. “He’s practicing being in peoples faces to protect his backside to prep for prison,” said one of the messages. Another, a retweet, observed: “Soon Jeff Noviztky [sic], a ‘Good Friend’ of @Ty_Hamilton is going to toss @lancearmstrong out of the bistro called freedom.”

It’s tempting to write this stuff off as mere towel-snapping by a disgruntled jock and his online pals, but Landis’s cyber-heckling could seriously backfire, particularly if he’s called upon to testify in court. Reportedly, Landis is a plaintiff in a federal whistle-blower lawsuit filed against Armstrong and his former U.S. Postal teammates, and he’s a potential witness for the government should a current grand jury investigation of Armstrong result in fraud or perjury charges. (The inquiry began shortly after Landis accused Armstrong of cheating in 2010, allegations that were made public after The Wall Street Journal obtained a letter Landis had written to cycling’s governing body, the International Cycling Union. Armstrong has steadfastly denied any wrongdoing.) Landis also says he’s the subject of an ongoing FBI investigation into fundraising activities by his Floyd Fairness Fund.

With litigation on the table, leaving a trail of hostile tweets might not be the brightest idea. “No good can come from this, either as a whistle-blower or as a federal witness,” says Bill Lawler, a former federal prosecutor who’s now a partner at the Washington, D.C., offices of Vinson and Elkins. “As a prosecutor, I want someone who’s credible and not biased, and not going to be viewed as someone with an ax to grind.”

Sandra Baron, executive director of the Media Law Resource Center in New York City, agrees. “Tweeting under assumed names, name-calling, and similar antics opens the door (and pretty widely) for the argument that his animus toward Armstrong is so great as to taint everything he says about Armstrong,” Baron wrote in an e-mail.

Armstrong and his inner circle have taken notice, and they’re not pleased. “Twitter is a public forum,” Armstrong told Outside in an e-mail. “Using it to publicly and intentionally attack and humiliate people of diverse backgrounds is offensive to me and many others.”