You can now read 5 articles in a month for free on BostonGlobe.com. Read as much as you want anywhere and anytime for just 99¢.

Cyberattacks on banks growing larger

American Express customers trying to gain access to their online accounts Thursday were met with blank screens or an ominous ancient type face. The company confirmed that its website had come under attack.

The assault was just the latest in an intensifying campaign of unusually powerful attacks on US financial institutions that began in September and have taken dozens of them offline intermittently, costing millions of dollars.

Continue reading below

JPMorgan Chase was taken offline by a similar attack earlier this month. And last week, a separate, aggressive attack wiped data from South Korea’s banks and television networks.

Corporate leaders have long feared online attacks aimed at financial fraud or economic espionage, but now a new threat has taken hold: attackers, possibly with state backing, who seem bent on destruction.

‘‘The attacks have changed from espionage to destruction,’’ said Alan Paller, director of research at SANS, a cybersecurity training organization. ‘‘Nations are actively testing how far they can go before we will respond.’’

Security specialists who studied the attacks said it was part of the same campaign that took down the websites of JPMorgan Chase, Wells Fargo, Bank of America, and others over the past six months. A group that calls itself the Izz ad-Din al-Qassam Cyber Fighters has claimed responsibility for those attacks.

The group says it is retaliating for an anti-Islamic video posted on YouTube last fall. But US intelligence officials and industry investigators say they believe that the group is a convenient cover for Iran.

North Korea is considered the most likely source of the South Korean attacks, although investigators are still struggling to follow the digital trail, a process that could take months. The North Korean government of Kim Jong Un has openly declared that it is seeking out online targets in its neighbor to the south to exact economic damage.

Neither country is considered a superstar in this area. But the appeal of digital weapons is similar to that of nuclear capability: It is a way for an outgunned, outfinanced nation to even the playing field. ‘‘These countries are pursuing cyberweapons the same way they are pursuing nuclear weapons,’’ said James A. Lewis, a cybersecurity specialist at the Center for Strategic and International Studies in Washington. ‘‘It’s primitive; it’s not top of the line, but it’s good enough and they are committed to getting it.’’

US officials are currently weighing their response options, but the issues involved are complex.

At a meeting of banking executives, regulators and representatives from the Homeland Security and Treasury departments in December, some attendees pushed the United States to hit back at the hackers, while others argued that doing so would only lead to more aggressive attacks, according to two people at the meeting.

Loading comments...
Subscriber Log In

We hope you've enjoyed your 5 free articles'

Stay informed with unlimited access to Boston’s trusted news source.

  • High-quality journalism from the region’s largest newsroom
  • Convenient access across all of your devices
  • Today’s Headlines daily newsletter
  • Subscriber-only access to exclusive offers, events, contests, eBooks, and more
  • Less than 25¢ a week
Marketing image of BostonGlobe.com
Marketing image of BostonGlobe.com
Already a subscriber?
Your city. Your stories. Your Globe.
Yours FREE for two weeks.
Enjoy free unlimited access to Globe.com for the next two weeks.
Limited time only - No credit card required!
BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.
Thanks & Welcome to Globe.com
You now have unlimited access for the next two weeks.
BostonGlobe.com complimentary digital access has been provided to you, without a subscription, for free starting today and ending in 14 days. After the free trial period, your free BostonGlobe.com digital access will stop immediately unless you sign up for BostonGlobe.com digital subscription. Current print and digital subscribers are not eligible for the free trial.