When it rains, it pours.

More bad news has emerged from SuperValu, which reported Monday that another cyberattack may have compromised customer data. According to the company -- which announced in August that it had been attacked between June 22 and July 17 -- in late August or early September 2014, an intruder installed malware on a portion of its computer network that processes payment card transactions at some of its Shop 'n Save, Shoppers Food & Pharmacy, and Cub Foods owned and franchised stores.

The company believes this breach to be separate from the one previously reported. After uncovering the attack, the company began taking steps to secure the network, and it believes it has eradicated the malware. Thus far, the investigation into the second attack has not turned up any evidence that cardholder data was stolen.

"We care greatly about our customers, and the safety of their personal information will continue to be a top priority for us," SuperValu president and CEO Sam Duncan said in a press release. "We've taken measures to install enhanced protective technology that we believe significantly limited the ability of this malware to capture payment card data and we will continue to make these investments going forward."

According to SuperValu, its use of "enhanced protective technology" limited the malware's ability to capture data from payment cards. Though there is no evidence that the attacker stole any data, the company acknowledges that data could have been swiped from checkout lanes at four Cub Foods franchised stores.

The four stores are located in Hastings, Shakopee, Roseville (Har Mar), and White Bear Lake, Minn. The security technology that mitigated the malware in other stores had not been fully implemented in those locations. As a result, the malware may have been able to capture customer information between Aug. 27 and Sept. 21, according to the company.

"It's clear from these latest disclosures that these attacks are not going away," says Rob Sadowski, director of technology solutions at EMC's RSA security division. "The card brands and law enforcement have published very public warnings about attacks targeting the grocery business as early as April of 2013. We continue to see attackers going after the biggest and highest-profile targets because they feel they can succeed, and grocers are some of the most lucrative because of the high volume of payment card transactions they handle."

Until retailers and other firms adopt point-to-point encryption and tokenization, "as well as improve their ability to detect and respond to attacks in progress with better network and endpoint visibility and forensics, these breaches will continue to affect the retail sector and any others which handle valuable payment card data," he says.

SuperValu believes the recently discovered malware was not installed at and did not affect any of its Farm Fresh or Hornbacher's stores, any of its owned or licensed Save-A-Lot stores, or any of the independent grocery stores supplied by SuperValu through its Independent Business network other than the affected Cub Foods franchised stores.

The company has notified and is cooperating federal law enforcement officials. Some stores owned and operated by Albertson's LLC and New Albertson's Inc. experienced a related criminal intrusion that is believed to have occurred around the same time.