Question: What WikiLeaks using whistleblower is notable for having a hacking organization with a user base of over 1,800,000?

Context:
GameDev.net
GameDev.net is a website dedicated to game development, founded by Kevin Hawkins, Dave Astle, and Michael Tanczos among others, in 1999.
 It serves as a central trade resource and media outlet for the computer and video game industry, with particular regards to hobbyist and independent developers.
 The site features daily news, articles, forums, job listings, product reviews, book reviews, contests, and regular columns.
 The site contains many tutorials for hobbyists and professionals alike with a noticeable focus on computer programming.
 GameDev.net is visited by a variety of people, including both professionals and hobbyists, and has a highly active user base.
 Previous site wide polls indicate that the site's demographics are predominantly male, with roughly 44.5% of its user base being under 21, and 44.1% of its user base in the 22-30 range.
 The site also has a popular forum which boasts advanced topics ranging from artificial intelligence and DirectX programming to the off-topic lounge.
Friends of WikiLeaks
Friends of WikiLeaks, sometimes reduced and stylized as FoWL, was a surveillance-resistant social network site created in support of WikiLeaks.
 Founded in May 2012, the site was intended for those who support WikiLeaks and its activities to perform advocacy.
 In contrast to more traditional forms of social networking, FoWL aimed at bringing together like-minded people who do not yet know each other.
 To achieve this goal, the site would ask about the language the user speaks as well as any preferences in the ways of hobbies or other activities.
 The site would then find six friends who share the user's views within your country, and another six from other parts of the world who speak your language.
 If one of those friends cancelled their account or became inactive, a new friend would be matched to the user's circle and would replace the previous inactive one.
Ashley Madison data breach
In July 2015, a group calling itself "The Impact Team" stole the user data of Ashley Madison, a commercial website billed as enabling extramarital affairs.
 The group copied personal information about the site's user base and threatened to release users' names and personally identifying information if Ashley Madison was not immediately shut down.
 On 18 and 20 August, the group leaked more than 25 gigabytes of company data, including user details.
Growth hacking
Growth hacking is a process of rapid experimentation across marketing channels and product development to identify the most efficient ways to grow a business.
 Growth hacking refers to a set of both conventional and unconventional marketing experiments that lead to growth of a business.
 Growth hackers are marketers, engineers and product managers that specifically focus on building and engaging the user base of a business.
 Growth hackers often focus on low-cost alternatives to traditional marketing, e.g. using social media, viral marketing or targeted advertising instead of buying advertising through more traditional media such as radio, newspaper, and television.
Sigurdur Thordarson
Sigurdur Thordarson (Sigurður Ingi Þórðarson) was born in 1992 in Reykjavík.
 He is known for his involvement with the whistleblowing organization WikiLeaks, as well as his interactions with the Federal Bureau of Investigation (FBI).
 In 2010 he was arrested for stealing and leaking classified information about the bank structure in Iceland.
 He obtained the information from a lawyer that aided wealthy people in tax evasion, whose name was Gunnar Gunnarsson.
 Gunnar worked for an investment firm called Milestone ehf.
 Gunnar obtained Sigurdur's services to set up computer systems and delete data.
 After Sigurdur was arrested he was introduced to Julian Assange, the editor and founder of WikiLeaks.
 Sigurdur started his time there in early 2010, and participated in preparing many of WikiLeaks's biggest leaks.
 After a year in WikiLeaks service Sigurdur was suspected of embezzling funds from the WikiLeaks online store.
 WikiLeaks filed criminal charges against Sigurdur with the Metropolitan Police of Iceland, who investigated the case and later dropped it due to lack of evidence.
 Sigurdur later plead guilty to the embezzlement along with other economic crimes, in 2013.
 Sigurdur was ordered to pay the victims 15 million ISK (roughly $115,000)
Installed base
Installed base (also install base, install[ed] user base or just user base) is a measure of the number of units of a product or service that are actually in use, especially software or an Internet or computing platform, as opposed to market share, which only reflects sales over a particular period.
 Although the install base number is often created using the number of units that have been sold within a particular period, it is not necessarily restricted to just systems, as it can also be products in general.
 Because installed base includes machines that may have been in use for many years, it is usually a higher figure than market share .
 Many people see it as a more reliable indicator of a platform's popularity.
Online gaming in China
Online gaming in China represents one of the largest and fastest growing Internet business sectors in the world.
 With 457 million Internet users currently active in the PRC, the country now has the largest online user base in world, of which two-thirds engage in online game play.
 The average online gamer in China is relatively young (18 to 30 years old), male, and has at least completed a secondary level of education.
 Demographically the online gaming user base in China is very similar to base of China Internet users, most of whom live in larger cities.
HackThisSite
HackThisSite.org, commonly referred to as HTS, is an online hacking and security website founded by Jeremy Hammond, with the site being maintained by a members of the community after his departure.
 It aims to provide users with a way to learn and practice basic and advanced "hacking" skills through a series of challenges in a safe and legal environment.
 The organization has a user base of over 1,800,000.
 The actual number of active members is believed to be much lower.
 The most users online at the same time was 1,995 on February 5, 2012 at 2:46:10 AM CST.
Jeremy Hammond
Jeremy Hammond (born January 8, 1985) is a political hacktivist and computer hacker from Chicago.
 He was convicted and sentenced in November 2013 to 10 years in US Federal Prison for hacking the private intelligence firm Stratfor and releasing the leaks through the whistle-blowing website WikiLeaks.
 He founded the computer security training website HackThisSite in 2003.
Owen Walker
Owen Thor Walker (online pseudonym AKILL) is a computer hacker living in New Zealand, who was discharged without conviction despite pleading guilty to several charges of 'cybercrime'.
 In 2008 he admitted to being the ringleader of an international hacking organization estimated to have caused $26 million worth of damage.

Answer: Jeremy Hammond