Is it possible for someone outside an organization to remove links?

[Stol]

The other day I used the Explorer tool to check my links. I checked again today, and the strongest links, which have been on my site for many months, are no longer listed on the report. I'm wondering if there has been some malicious activity. If the links have been removed, how do you get them back?

[JarnoNijzing]

are those links still active according to the websites and for instance google? In the netherlands we got startpagina.nl which uses a linkpool so that every 3 of 5 months new links will appear on their page. It could be that your very important links are used in a linkpool.

Or the links are still there but the bot maybe missed them. U should definetly check google:

link:wwww.mysite.com / link:http://www.mysite.com / link: www.mysite.com

If it appears in Google and you check it on the page itself if its true you'll have your answer

[NakulGoyal]

I would download the backlinks from Google Webmaster Console or Open Site Explorer and see if those links are there. Maybe some other links appeared to the tool as stronger. IN Google Webmaster Console, you can also find last found date which is helpful.

Now trying to answer your question: Is it possible for someone outside an organization to remove links?
It is technically possible for a competition to reach out to people who are linking to you and figure out a way to get those links removed and / or changed to their own websites. Is it happening in your case, the only way to check would be to find 10-20 examples of sites that were linking to you and see what happened. If needed, reach out to the website owner to find out.

[KeriMorgret]

Are you saying that what had been identified by the SEOmoz tools as a valuable link that is on your site is no longer identified as a valuable link? Or has the link on your site itself disappeared? If the link itself has disappeared, you need to investigate with your IT department. If it's that SEOmoz no longer identified the link as strong, send an email to help@seomoz.org and ask our help team about it.

Did that help, or did I misunderstand your question?