The damage caused by a Canadian navy officer who sold secrets to Russia is still being assessed, a director with the Canadian Security Intelligence Service told a sentencing hearing Thursday.

Sub.-Lt. Jeffrey Paul Delisle, 41, pleaded guilty in October to breach of trust and passing information to a foreign entity that could harm Canada's interests. A provincial court in Halifax heard that Delisle was paid nearly $72,000 for providing Russian agents with classified information.

Assessing the fallout of Delisle’s actions is “an ongoing process,” Michelle Tessier, director general of internal security at CSIS, told the sentencing hearing.

"Knowing this took place over a five-year period is extremely concerning, especially (because) there is a lot we still don't know,” she said.

"Mr. Delisle volunteered. He wasn't even recruited. For us, that has a significant impact."

Tessier said a lot of resources are being used to assure Canada’s allies, including the United States and Great Britain, that their national security has not been compromised.

"There's a risk we might be cut off of certain intelligence," Tessier said, adding that the worst-case scenario could result in the loss of lives.

Before his arrest last year, Delisle had sent two documents to the Russians that could potentially identify sources working for CSIS, Tessier said.

Crown attorney Lyne Decaire told the court that Delisle offered his spy services to the Russian Embassy in Ottawa and was asked to provide a “manuscript” each month with information relevant to Russia. He received 23 payments from the Russians between 2007 and 2011, totalling $71,817.

Delisle searched references to Russia on government computers, copied the classified information on a floppy disk at work and then transferred it onto a memory stick on an unsecure computer system, Decaire said. The navy officer would then copy the information into an email address he shared with the Russian agent, so that emails were never sent from his inbox.

Decaire said Delisle travelled to Brazil in 2011 to meet a Russian agent and aroused the suspicions of Canada Border Services Agency upon his return.

The agency noted that Delisle didn’t seem to know much about the tourist sites he supposedly visited in Brazil, had no tan and was carrying thousands of U.S. dollars in cash and three prepaid credit cards.  

Delisle was arrested on Jan. 13, 2012.

Under questioning from defence lawyer Mike Taylor, Brig-Gen. Rob Williams, director general of military signals intelligence, admitted that there were security lapses at HMCS Trinity, where Delisle worked.

"There were problems, yes," he told court. "Things were missed."

At one point during the court proceedings, Delisle told Judge Patrick Curran that he agreed with the statement of facts presented in court.

Delisle is the first person to be sentenced under Canada's Security of Information Act, introduced after the Sept. 11 attacks in the U.S. He faces a maximum sentence of life in prison.

With files from The Canadian Press and a report from CTV Atlantic