Buying a home in the Bay Area has gotten a lot tougher over the past week. Since Wednesday, Aug. 9, thousands of homebuyers, sellers and real estate agents haven't been able to access new property listings or open houses on Multiple Listing Service sites due to a cyberattack on MLS software provider Rapattoni Corporation.

The systemwide outage has impacted listing sites in markets nationwide, including San Francisco and the north bay counties of Marin, Sonoma, Napa, Solano and Mendocino.

Service is not expected to be restored until at least Thursday, Aug. 17, the San Francisco Association of Realtors posted on Tuesday morning.

The Federal Bureau of Investigation is reportedly investigating the cybersecurity attack – a form of cybercrime that encrypts the victim’s data and demands a ransom for its release, according to Housingwire.

Based in southern California, Rapattoni provides software products and services for real estate associations and MLS organizations that operate local databases on which real estate listings are posted. The information from these local databases then gets syndicated to real estate sites like Zillow and Redfin.

According to the company, more than 300 real estate associations nationwide use Rapattoni and about 5% of the nation's MLS databases use its software system.

Unable to add new listings or update listings with price changes or open houses, members of the San Francisco Association of Realtors scrambled for days to move their listings to other sites, such as Zenlist and Realtor.com. On Monday, the organization announced it would be moving away from " temporary workarounds."

"Our focus … will be to support this week's Broker Tour and to prepare for how to bring the MLS back online with minimal disruptions and unwanted side effects," the organization posted.

The association, which includes more than 4,500 members, had 141 open houses scheduled for this week's broker tour, an event for real estate professionals featuring newly active properties on the market. The listings were moved to a downloadable PDF on its website.

On the Peninsula, the 17,000 Realtor members of Sunnyvale-based MLSListings Inc. in San Mateo, Santa Clara, Santa Cruz and other neighboring counties were not affected by the Aug. 9 Rapattoni cyberattack and resulting outage.

Dave Wetzel, MLSListings CEO, said his organization uses two different systems provided by Oakland-based CoreLogic and Black Knight Financial Services, based in Jacksonville, Florida. Neither was affected by the outage.

Wetzel said his organization offered use of its systems to affected Realtors in San Francisco and the north bay. If they did take advantage of the systems, only the property and information search functions would have been available to them, Wetzel said.

“We wanted to pull together and help out Realtors in the affected areas,” Wetzel said.

The Silicon Valley Association of Realtors, which includes 5,000 members in the Peninsula and south bay, uses MLSListings and was not impacted by the shutdown.

The association posted an alert from MLSListings, however, that members could be viewing out-of-date listing data on listings showing up from the San Francisco and north bay county areas that use Rapattoni.

"Until this situation is corrected, MLSListings is highly recommending that agents connect with the listing agent of these listings to ensure you are working with the most up-to-date information on the status, price and showing instructions," the Silicon Valley Association of Realtors posted.

Rapattoni tweeted on Saturday that it will be working around the clock until the matter is resolved.

"We are continuing to investigate the nature and scope of the cyberattack that has caused a system outage, and we are working diligently to get systems restored as soon as possible. … We will continue to update you and keep you informed of our efforts."

Freelance writer David Goll contributed to this article.