Valentin Mazlevski, 40, a Belorussian immigrant who moved to Israel in 1996, was the first Jewish-born Israeli to be charged for having ISIS ties, according to the Shin Bet domestic security service.
He was arrested in February 2017, a few weeks after a failed attempt to fly from Israel to Turkey, from where he allegedly planned to cross into Syria to join ISIS forces.
The Nazareth district court said in its ruling that Mazlevski had "one goal: to join the organisation".
He acted "out of identification with the organisation's ideology," in the process "violating the law and endangering the state's security," it said.
In 2000, while performing compulsory service in the Israeli military, Mazlevski converted to Islam after meeting the Israeli Arab Muslim woman who would become his wife and mother of his five children.
Mazlevski, who became interested in ISIS and frequently viewed its online content in recent years, joined the jihadist group's internet forums, Israeli authorities said.
Both plans failed.
Shin Bet also revealed Monday it had arrested three Arab Israelis for allegedly planning to carry out shooting attacks at the Al-Aqsa mosque compound in east Jerusalem or against Jewish or Christian prayer sites.
"Two cell members support the murderous ideology of the ISIS terrorist organisation and sought to perpetrate attacks in the context of this support," the Shin Bet said in a statement.
Several Arabs from northern Israel have been arrested for alleged links with ISIS and around 20 Arab Israelis are now believed to be among its ranks in Syria and Iraq.
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