This has been a serious problem in our country since the 1960s, and this report in the New York Times indicates one method of addressing it.

An excerpt.

LONDON — Convicts in British prisons who preach terrorism and extreme ideology to fellow inmates will be held in high-security “specialist units,” the government announced on Monday, amid efforts to crack down on Islamic radicalization in jails.

The announcement reflects an emerging trend in Europe to isolate terrorism convicts and influential extremists from the rest of the prison population. Prisons are often regarded as potential breeding grounds for would-be terrorists, particularly for young offenders serving sentences for crimes unrelated to terrorism but who nonetheless fall under the spell of older, charismatic inmates.

Last week, Anjem Choudary, one of Britain’s best-known Islamist activists, was found guilty of inviting support for the Islamic State. He could face a lengthy prison term.

“There are a small number of individuals, very subversive individuals, who do need to be held in separate units,” Elizabeth Truss, who took office last month as justice secretary and who made the announcement, told the BBC. Under the plan, prison wardens, or governors, will also be instructed to remove extremist literature and tighten the vetting of prison chaplains.

The announcement was in response to a government review of Islamist extremism in prisons, a summary of which was also published on Monday.

The review, led by a former prison governor, Ian Acheson, recommended placing in specialist units a “small subset of extremists who present a particular and enduring risk to national security through subversive behavior, beliefs and activities.”

Antiterrorism legislation passed after the July 7, 2005, bombings in London, which killed 56 people, including four bombers, criminalized “those who glorify terrorism, those involved in acts preparatory to terrorism and those who advocated it without being directly involved,” the review noted.