PNC Bank has warned customers its websites are getting hit with high traffic consistent with computer attacks.

In an email sent to nearly 5 million customers, PNC Bank says the traffic is meant to cause delays for legitimate online banking customers. It says other banks are experiencing similar traffic spikes but did not identify them.

PNC Bank says that for several weeks it has worked to block the traffic and maintain online and mobile banking access for the vast majority of its customers. The company says it may have blocked access for a small percentage of its legitimate customers for an extended period.

PNC Bank assured its customers that its website uses encryption to protect customer information and accounts.