Shares in London-listed cyber security group Sophos were down by nearly 7% on Tuesday morning after private equity firm Apax revealed it would sell around half its holding.
Apax is to sell 51 million shares, representing more than 10% of Sophos's market capitalisation.
The private equity firm raised £315m by selling the shares at 616p, a discount of nearly 5% on Sophos’s share price as at the close of trading on Monday.
Shares were trading at 601.5p as at 0930 GMT.
The stock is still up by around 140% over the past year, with rising worries over cyber attacks having driven the share price higher.
Sales of Sophos’s anit-virus and encryption software to businesses are seen as benefiting from high-profile cyber attacks such as this year’s incidents involving so-called WannCry and Petya malware.