Each network has its own system for delivering screeners to TV critics and reporters — from physical DVDs to videos hosted on their press sites. But as piracy concerns mount, those methods are changing in favor of more secure alternatives.

Last month, HBO — after suffering a cyber attack and in two separate incidents, watching two episodes of its most popular show, “Game of Thrones,” be leaked online ahead of their premieres — migrated its screeners from its own private portal, HBO ViP, to a new site, Screeners.com — a hub through which TV critics and reporters can access shows from multiple networks. Hulu, Amazon, and El Rey Network have also moved their episodes to the site. Fox, just weeks before the start of the new fall broadcast season, shut down its proprietary site, Fox Flash, and moved its shows to a new proprietary site, Screeners.Fox. And Starz recently moved episodes of “Outlander” off of its screening site and began distributing them to press through cloud-based software DAX. Multiple network publicity executives declined to comment on the record about changes to their screener distribution, but several acknowledged privately that security was one factor.

The moves are the latest evolution in a hodgepodge distribution network that attempts to balance security concerns with viewer experience. But when the two come into conflict, security almost always win out.

“Security is front of mind for everyone” said Jared Vincenti, product manager for Screeners.com. “We get put through the paces by every prospective client’s security department.”

More than a year in development, Screeners.com was created by MediaSilo, a company that handles secure video distribution for multiple TV-industry clients — and built proprietary screening sites for several of them after its success in creating a system for placing security watermarks on video. (The company declined to speak about its client roster.)

Several network publicity executives echoed Vincenti’s assertion that security is a greater concern than usability — hence the visible watermarks that often appear on digital screeners that prompt grumbling from critics perturbed at having to watch episodes with such unsubtle visual interference.

For some shows, security has blown all other concerns out of the water. After four “Game of Thrones” episodes that leaked to piracy sites in 2015 were traced back to screeners, HBO stopped distributing episodes of the series in advance of airing, altogether. (The two episodes leaked from the most recent season were traced back to employees of a vendor working with HBO partner Sky India and an employee error at HBO’s European services.) Several seasons ago, ABC stopped distributing screeners for “Scandal” and other shows from Shonda Rhimes in response to the prolific executive producer’s concerns regarding spoilers.

But in other cases, press sentiment has won out over security. Several networks — including the five broadcasters — still send out DVD screeners regularly. Many critics, particularly older members of the Television Critics Association, refuse to watch digital screeners, and have told networks that they will not write about shows without access to a physical copy. But network publicity executives noted that, in addition to being costly to produce and ship, physical screeners are less secure than digital versions. Physical screeners, for instance, are not always watermarked with information that identifies the recipient the way that most digital screeners are.

The shift toward digital distribution has stemmed the flow of pre-premiere leaks.

“Television content used to appear online before its release date more often,” says Chris Anderson, head of film and TV for the anti-piracy firm MUSO. “The way that content was distributed was by DVD rather than behind locked [digital] screeners. It seems to be a bit more secure now.”

Digital screening systems are not without their own security issues, however. When developing Screeners.com, Mediasilo found that a vast majority of users who access press screening sites keep a document with a list of log-in information for each individual site — a significant security risk. “What’s meant to be a security system is actually undercut by the fact that people have way too many of these things to keep track of,” says Vincenti. Screeners.com does away with password-protected log-in, instead using a newer system that sends a customized link to the user’s email inbox every time he or she attempts to access the site.

Meanwhile, piracy of television programming is on the rise. In an April report, MUSO tallied 62.7 billion incidents of television content infringement worldwide in 2016, up from 45.1 billion in 2015. HBO, the Walt Disney Co., and Netflix have all suffered significant security breaches this year that saw their television programs leak online.

“It’s absolutely huge,” Anderson said of piracy and overall cybersecurity concerns. “It’s a real problem for the industry.”

In that environment, networks are likely to continue to treat their screeners with an excess of caution.