Hackers have enjoyed a mixed reputation over the last thirty years, romanticised and demonised in equal measure. Variously portrayed as weird, anti-social nerds or the revolutionaries of the digital age (and sometimes both), their exploits have often ended with threats of imprisonment, as shown this week in the release of Hector "Sabu" Xavier Monsegur, a LulzSec hacker turned informant for the FBI.

With hacking now a regular feature of the news cycle it’s worth looking back on some of the pioneers. Whether you admire or admonish them, some of the heists pulled off by the hackers are impressive, showing what a few men (and it is mostly men) armed with keyboards can do to multinational organisations and some of the world’s strongest governments.

1) Legion of Doom

Active: 1980s to 2000
Based: Texas, US

Also known as Legion of Hackers, LOD was founded by a man going by the name Lex Luther, and in addition to hacking produced tech journals on the subject, some of which are still available online. The group was chaotic and dysfunctional, sharing members with Masters of Deception with whom they would later conduct the Great Hacker War, but during the 90s it was legendary in the underground scene of hackers.

Most prominent among these was hacker Mark "Phiber Optik" Abene, a brash New Yorker who would later be expelled from the group after a quarrel with Chris "Erik Bloodaxe" Goggans, following a feud between the pair. LOD members would later go on to form Comsec Data Security, a professional firm that hired its services out to the sort of companies the hacking underground used to target.

2) Masters of Deception

Active: Late 1980s to early 1990s
Based: New York, US

Formed as a snub to LOD and billing themselves as the next generation of hacker, MOD variously meant Masters of Disaster or Mothers on Drugs before the reverse acronym settled on a popular meaning. Created by Paul "Scorpion" Stira, Eli "Acid Phreak" Ladopoulos and Mark "Phiber Optik" Abene, the group went on to recruit John "Corrupt" Lee, a black member of a New York street gang called the Decepticons, after the villains of Transformers.

Following Lee’s run in on hacking conference call in which one Texan demanded that someone "Get that n****r off the line", the hacker would keep tabs on LOD, and later phone tap Comsec. Shortly after Comsec discovered Lee was eavesdropping on them the FBI would indict members of MOD on charges of illegal computer intrusion, resulting in the four main members all ending up in prison in early 1994.

3) milw0rm

Active: 1998
Based: New Zealand, Britain and the US

One of the more obscure entries on this list, little is known about the members of milw0rm, an international group of hacktivists who would break into the computers of Bhabha Atomic Research Centre (BARC) in Mumbai, India and decorate the nuclear facility’s website with a peace message.

The group began the attack by breaking into a string of computers around the world, eventually hacking into US military servers before they launched the attack on BARC. Aside from vandalising the website, the hackers also downloaded 5MB of information from the site – a more impressive amount before the turn of the millennium. The group disbanded shortly after the attack.

4) Anonymous

Active: 2004 to present
Based: Worldwide

Undoubtedly the most famous hacking group in the world, Anonymous has been involved in political protests against foes as diverse as the Church of Scientology, the Western music and the Tunisian government.

Starting life on the 4chan forums in 2004 before diverging into uncountable chapters, the group has gradually slit between those hacking "for teh lulz" and those with political agendas to push. Initially attacks tended towards the former persuasion, with raids on social network Habbo Hotel an infamous example of the group’s early history, but increasingly the group has been associated with radical and even revolutionary political movements such as Occupy.

A fuller list of their exploits can be found here.

5) Lulzsec

Active: 2011 to 2012
Based: Worldwide

In many ways the logical conclusion to Anonymous’ love of pranks, LulzSec emerged as a separate group in May of 2011, kicking off what they later termed "50 days of lulz". Formed after a hack on digital security firm HBGary, the group’s attack of media group Fox’s website begun a spree of cyber assaults, hitting cash points in the UK, and the websites of the US’ Public Broadcasting System and Sony.

Despite claims the group had dissolved after 50 days, attacks continued into 2012, with "Titanic Take-down Tuesday" seeing Minecraft, League of Legends, the Escapist and security company FinFisher all taken off the internet in a single day. Much of the information obtained in LulzSec attacks was posted online, yet there was no suggestion the group sought to profit from their activities.

Yet as hackers’ ability to cause damage had steadily increased, so had law enforcement’s powers for stopping them. On both sides of the Atlantic police began rounding up members of the group, most famously arresting Sabu in June 2011. LulzSec would still go on to participate in AntiSec, a series of hacks in collaboration with Anonymous, but after that the group seemingly fell apart, with several ending up in prison.

6) TeaMp0isoN

Active: 2010 to 2012
Based: Worldwide

Led by a hacker who goes by the name of Junaid "TriCk" Hussain, Team Poison has been one of the most narrowly political hacking groups ever to have existed, rarely breaching websites without an explicit message in mind. Their victims have ranged from the English Defence League to NATO, and even included former prime minister Tony Blair, in an attack Hussain would later be jailed for.

Self-defining as anarchists, the group also drew attention to itself when it hacked Blackberry in the summer of 2011, after the phone makers said they would cooperate with the authorities in investigating those who had rioted earlier in the year. "We are all for the rioters that are engaging in attacks on the police and government," the group said.

7) Syrian Electronic Army

Active: 2011 to present
Based: Middle East

While Bashar al-Assad was waging war on his own people, a loyal army of digital supporters was lining up to attack his critics online. For the most part SEA has resorted to bombarding American media with distributed-denial-of-service (DDoS), but they are also famous for seizing Twitter accounts of reputable sources and posting phony news stories.

Victims include the BBC, Associated Press and Qatari news group al-Jazeera. While their actions may seem trivial, a fake story claiming that Barack Obama had been injured in a White House bombing knocked $136bn off the New York Stock Exchange. The group is also said to target opposition within Syria, though details of that are understandably sketchy.