Judge Jose de la Mata took a statement on Friday via videolink from Assange at a London court about alleged espionage at the Ecuadorian embassy in the British capital, where he was granted asylum, Efe news reported.
Assange is being held in London during extradition proceedings at Westminster Magistrates Court brought by the United States.
A Spanish court previously opened a criminal case against Spanish security company UC Global, which worked in the Ecuadorian embassy during the seven years Assange was sheltered there.
The company allegedly worked for US intelligence and recorded the whistleblower while he was in exile.
In August, de la Mata accepted a procedure for the complaints and in September he ordered the arrest of UC Global owner David Morales.
The complaint focused on alleged acts of espionage by the Spanish company at the request of the US that included Assange and visits he received at the diplomatic headquarters, including former American politician Dana Rohrabacher.
UC Global took over security at the London embassy between 2015 and 2018, Morales allegedly had a significant capital increase, bought an expensive house and cars during the period.
The company allegedly put a microphone in a fire extinguisher in a room in the embassy where Assange held confidential meetings with his visitors, including his lawyers, doctors and diplomatic agents.
Morales is accused of taking Assange's fingerprints from a glass and taking photographs of visitors to the embassy.
The judge said the activities could amount to crimes against privacy, the privilege of attorney-client communications and money laundering.
Assange rose to international attention in 2010 after WikiLeaks published leaked military information provided by former United States Army soldier Chelsea Manning, which prompted the US government to launch a criminal investigation into the publisher.
In November that year, Sweden requested his extradition over allegations of sexual assault and rape, which he denied.
He also expressed concern that he would be extradited from Sweden to the US because of his role in the Manning leaks.
Assange surrendered himself to UK police around a month later and was held in custody for 10 days before being released on bail.
When he was unable to challenge the extradition proceedings, he breached bail and in August 2012 was granted asylum by Ecuador.
Sweden has since withdrawn its extradition request, but a UK arrest warrant remained in force as Assange had failed to surrender after breaking bail conditions.
( With inputs from IANS )