Symantec will acquire three companies: Riptech, a managed security services provider, for $145m (£93m); Recourse Technologies, a vendor of intrusion-detection software, for $135m (£86m); and SecurityFocus, a provider of a virus alert service, for $75m (£48m).
In another deal earlier this month, Symantec bought Mountain Wave, for $20m (£13m). Mountain Wave develops automated attack sensing and warning software.
"All of these acquisitions aim to address specific weaknesses in our portfolio," said John Schwarz, president and chief operating officer of Symantec.
The acquisitions continue the company's efforts to transform itself from a consumer-focused vendor to one that offers a variety of tools for corporate security managers.
Schwarz said that more than 60% of the $1.1bn (£702m) in revenue that Symantec reported for its financial year, which ended in March, came from sales to corporate users, compared with about 30% two years ago.
Pete Lindstrom, an analyst at Hurwitz Group, said the acquisitions would make Symantec one of the few IT security vendors to offer such a wide range of corporate tools.
Such one-stop shopping capabilities are crucial for users, according to Lindstrom. "What this does is to elevate the buying decision around securing an enterprise, as opposed to considering individual products," he said.
But Michael Rasmussen, an analyst at Giga Information Group, said there is little evidence to show that users want all their security products from one vendor.