IRS building

The Internal Revenue Service has closed down its electronic filing PIN tool after noticing suspicious activity.

The IRS said Thursday that it saw automated attacks taking place with more frequency and has closed both the online tool on in addition to the toll-free phone service.

The IRS had detected such activity in February, finding that cybercriminals were using taxpayer information they had stolen elsewhere, along with an automated bot attack, to access more than 100,000 e-File PINs using the online tool (see IRS Detects Attack on Electronic Filing PIN App).

However, the IRS decided at the time to leave the service available online since it was the middle of tax season and links to it were embedded in nearly all commercial tax prep software programs.

The IRS instead added more defenses to its processing systems to scrutinize any tax returns sent with an e-File PIN more closely. But the IRS has recently seen more automated attacks occurring with increasing frequency, prompting the shutdown.

The IRS said the shutdown would not have an impact on most taxpayers.