L0pht Heavy Industries (pronounced "loft") was a famous hacker collective located in the Boston, Massachusetts area between 1992 and 2000.
The "Ø" in its name represents a zero, recalling the slashed zeroes that were used on old teletypewriters, so its normal on-line name, including its domain name, is "l0pht" (with a zero), not "lopht" (with an O) or "lØpht" (with a slashed letter O), which by that time would not have been a valid domain name.
Along with the significance of the "Ø", the name was not without meaning. Some of the founding members of the L0pht shared a common loft apartment space in Boston, from where they inter-connected and experimented with their own personal computers as well as equipment purchased from the Flea at MIT, and items garnished from dumpster diving local places of interest.
In 1998, representatives from the L0pht famously testified before the Congress of the United States that they could shut down the entire Internet in 30 minutes.
In January 2000, L0pht Heavy Industries merged with the startup @stake, completing the L0pht's slow transition from an underground organization of dubious legality into a licit "whitehat" computer security company.
Symantec announced its acquisition of @stake on September 16, 2004, and completed the transaction on October 9 of that year.