Enron stock rose nearly 6 percent on Wednesday after it announced that it had purchased Boston pharmaceuticals. 

It is the largest single transaction in the company’s history.

Enron also said that it would pay up to $20 billion in fines and penalties in connection with the incident. 

The announcement comes after the company said it was looking into “serious concerns” about the security of a computer server owned by Boston and a security firm, after Enron employees discovered the server had been infected with malware.

Enrons shares have risen more than 15 percent this year.

The purchase is the biggest of several recent acquisitions of pharmaceuticals that have helped boost the company in the months since it went bankrupt in 2008.

Last week, Enron announced that its stock would be traded on Nasdaq.

Enos shares have surged more than 200 percent this month after the merger with Enron was completed. 

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