Billtrust,  the B2B payments provider is still recovering from a ransomware attack that began last week.  The company said it is in the final stages of bringing all of its systems back online from backups.

Billtrust is a cloud-based service that lets customers view invoices, pay, or request bills via email or fax. In an email sent to customers today, Billtrust said it was consulting with law enforcement officials and with an outside security firm to determine the extent of the breach.

In an interview with KrebsOnSecurity on Monday evening, Billtrust CEO Steven Pinado said the company became aware of a malware intrusion on Thursday, Oct. 17. The company has since stop the malware activities on its systems.

Billtrust recently partnered with Visa to launch the Billtrust Business Payments Network, an effort to digitize payments between businesses.