Sigurdur Thordarson

Sigurdur Ingi Thordarson (Icelandic: Sigurður Ingi Þórðarson) (born 1992), commonly known as Siggi hakkari ("Siggi the Hacker"), is an Icelandic convicted criminal and FBI informant against WikiLeaks. He is known for information leaks, multiple cases of fraud and embezzlement, sexual solicitation of minors and adults. He has multiple convictions for sexual offences.

In 2010, at the age of 17, he was arrested for stealing and leaking classified information about Icelandic financial companies. After his arrest, Kristinn Hrafnsson introduced him to Julian Assange, the editor and founder of WikiLeaks, and he worked as a volunteer for the organization between 2010 and 2011. In 2011, Thordarson contacted the FBI and offered to become an informant, turning over numerous internal WikiLeaks documents and hard drives in the process. WikiLeaks accused him of having embezzled $50,000 from the WikiLeaks online store to which he pleaded guilty along with other economic crimes against other entities. He was also accused of using Julian Assange's name in legal documents.

In June 2021, in an interview with Icelandic newspaper Stundin, Thordarson admitted that he had fabricated testimony he made against Julian Assange in the case in which the US sought Assange's extradition from the UK. Thordarson was a key witness whose testimony was crucial to the US case, according to numerous news organisations, including the German public broadcaster Deutsche Welle, The Hill, Der Spiegel and The Intercept. The Washington Post disagreed, writing that Thordarson's testimony was not part of the core allegations.

In the 2024 documentary A Dangerous Boy, directed by Ole Bendzen and produced by Academy Award-nominated Søren Steen Jespersen, it is alleged that the article claiming Thordarson admitted to lying was orchestrated and funded by WikiLeaks. Journalist Kristjón Kormákur, who has authored several articles about Thordarson, stated that he and Bjartmar Alexandersson were hired to investigate Thordarson, which ultimately led to the publication of the article. Thordarson has noted on his personal website that he does not admit to lying anywhere in the article or in the recordings of the interview; the claim appears only in the headline. WikiLeaks and Bjartmar Alexandersson declined to participate in the documentary, and the editor-in-chief of Stundin (now Heimildin) declined to comment on the allegations. Bjartmar stated in the documentary that he would not be allowed to participate unless WikiLeaks approved. When informed that WikiLeaks had hired journalists to produce the article, Thordarson responded: "Interesting".

Thordarson grew up middle-class in Reykjavik with a younger sister. He began hacking at age 12 and joined WikiLeaks in February 2010 when he was 17 years old and in high school. He went to university to study computer science and psychology, but says he was suspended for hacking.

Thordarson began leaking information about the Icelandic banking system to the media in late 2009. This included information about individuals in the Icelandic banking system, information that showed that individuals were committing illegal acts in relation to banking. One of the leaks by Thordarson concerned a case called "Vafningsmálið." It involved Bjarni Benediktsson during his time as an MP. Bjarni reported that the case was only a political smear campaign. The information published by Icelandic news media obtained from Thordarson also showed that one of the country's biggest football stars, Eiður Guðjohnsen, was deeply indebted and almost bankrupt.

After the information was published, Eiður sued the local newspaper DV for publishing this information. DV lost the case in a lower court, but won an appeal to the Supreme Court of Iceland, stating that the information was a matter for the public. Amongst other information that Thordarson admitted to have leaked in an interview with the Rolling Stone magazine was information about local businessman Karl Wernersson. He was the owner of the Milestone ehf that was the investment company from which Thordarson stole most of the information. Other names in the documents leaked by Thordarson included information about Birkir Kristinsson, who had recently been convicted of economic crimes while working for Glitnir bank. Some speculate that information from Thordarson was used as evidence in that case, Thordarson also leaked a classified report about one of the bigger aluminum plants in Iceland. The report stated that the plant was paying 1/4 of what other aluminum plants in the world are paying for electricity.

Other information leaked by Thordarson contained information about other local business men such as Gunnar Gunnarsson, who also has been reported to assist football star Cristiano Ronaldo in tax affairs. Kristinn Hrafnsson thought Thordarson's leaks were "quite significant" and introduced him to Julian Assange. In 2013, Thordarson argued with Birgitta Jónsdóttir on Twitter over the release of the loanbooks of the Glitnir Bank. Thordarson said she had no involvement, but he claimed that he had given her the files years ago. In 2009, Thordarson arrived at the offices of the Special Prosecutor, who investigated the bank collapse in Iceland in 2008. Thordarson reportedly gave them all the information he had on Milestone and other local business men, however instead of using some of the information obtained from Thordarson in investigation the investigators decided to sell the information. The case against the two police officers was later dismissed, and it has been reported that the investigators made roughly 30 Million ISK ($250.000) from the documents.