Updated

Officials with Naval Criminal Investigative Service have determined that about 500 members of the Marines United Facebook group followed a link to a drive containing nude and compromising photos of female Marines and other women, the commandant of the Marine Corps said Tuesday.

Speaking before the Senate Armed Services Committee in a hearing that was partially closed to receive classified testimony, Gen. Robert Neller said that while the number of individuals apparently involved in this illicit photo-sharing is a subset of the 30,000-member group, the actions stem from a troubling mindset of some in the Corps.

"This issue of denigration of women, objectification of women, misogyny, just bad behavior is tied to the way some group of male Marines look at women in the Marine Corps," Neller said. "And I think we can fix that by holding those accountable."

The hearing, scheduled after news broke last week about photo-sharing, harassment of women and, in one case, the stalking of a female Marine by members of Marines United, was at times angry and emotional as lawmakers expressed their outrage. Several brought up similar reports from 2013 of Facebook pages populated with active-duty Marines and veterans who would harass and target female service members, and post their photos so others could make sexual comments.

More From Military.com

"When you say to us, it's got to be different, that rings hollow," said Sen. Kirsten Gillibrand, a Democrat from New York. "Have you actually investigated and found anybody guilty? If we can't crack Facebook, how are we supposed to be able to confront Russian aggression? It is a serious problem when we have members of our military denigrating female Marines who will give their life for this country."

Despite then-commandant Gen. Jim Amos' receipt of a 2013 letter from Rep. Jackie Speier, a Democrat from California, complaining about the Facebook pages, Neller said he believed commanders then were ignorant of what was taking place online.

"Part of this is, I think victims were afraid to come forward, because if they came forward, they were going to be attacked tenfold on social media again," he said. "I think for those, that don't participate in this domain, I think we were ignorant. I'm trainable, and I accept responsibility for that."

Officials are still trying to determine how many women were victimized by the Marines United page and others like it. Acting Navy Secretary Sean Stackley told the committee that a dedicated tipline set up by NCIS had to date received 53 calls, from self-identified victims as well as those offering information to locate the pages and prosecute offenders.

The Marine Corps is now working with hosts such as Facebook and Google to shut down the pages in question and take damaging material offline, Neller said. How to prosecute offenders, both active-duty troops and veterans, may be a knottier problem.

Marine Corps officials have said active-duty perpetrators may be subject to Uniform Code of Military Justice articles 92, disobedience of an order, article 120c, broadcast or dissemination of photographs without consent, and 134, general violation. Under these orders, troops may be subject to non-judicial punishment or court-martial for Facebook activities. But it's possible these articles may not be enough, officials suggested.

Asked by Sen. Richard Blumenthal, a Democrat from Connecticut, if he wanted a new law on the books governing cyber-bullying, Neller said a Marine task force assembled this month would consider that.

"That's something we're going to get into with this task force, if there are provisions within UCMJ that may need to be more specific about this particular type of potential offense," he said.

For veterans, Neller and Stackley said, prosecution gets even more challenging, as laws governing online harassment and "revenge porn" vary from state to state.

Sen. Thom Tillis, a Republican from North Carolina, suggested creating a policy that could take away the benefits of veterans found to have engaged in internet harassment, nude photo-sharing and other activities.

"I want to look at other things we need to do to make this a very painful exercise for somebody found guilty of doing this as a member of the veterans community," he said.

As NCIS investigates and the task force determines a way forward, Neller said he is planning to focus on communicating with Marines that treating women in the service as unequal was unacceptable. He will travel to Camp Lejeune, North Carolina, Wednesday to meet with Marines and learn more about the mindset behind Marines United, he said.

"I think we addressed the action of individuals which is sexual assault or bullying," he said. "But I think the bigger issue within the culture is we haven't addressed the fact that all Marines are Marines."

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at @HopeSeck.