Exchange 2013 SP1 anti-malware updates not working

On a fresh install of Exchange 2013 SP1 anti-malware updates are not working. In event viewer we get following error:

Log Name:      Application

Source:        Microsoft-Filtering-FIPFS

Date:          3/21/2014 9:16:06 PM

Event ID:      6027

Task Category: None

Level:         Error

Keywords:     

User:          NETWORK SERVICE

Computer:      Mail.domain.local

Description:

MS Filtering Engine Update process was unsuccessful in contacting the Primary Update Path. Update Path: http://forefrontdl.microsoft.com/server/scanengineupdate

Event Xml:

<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">

  <System>

    <Provider Name="Microsoft-Filtering-FIPFS" Guid="{1BE3A000-EA09-4AB8-B0A0-30BBB6793D80}" />

    <EventID>6027</EventID>

    <Version>0</Version>

    <Level>2</Level>

    <Task>0</Task>

    <Opcode>0</Opcode>

    <Keywords>0x8000000000000000</Keywords>

    <TimeCreated SystemTime="2014-03-21T19:16:06.892015100Z" />

    <EventRecordID>163920</EventRecordID>

    <Correlation />

    <Execution ProcessID="2044" ThreadID="8468" />

    <Channel>Application</Channel>

    <Computer>Mail.domeniu.local</Computer>

    <Security UserID="S-1-5-20" />

  </System>

  <EventData>

    <Data Name="UpdatePath">http://forefrontdl.microsoft.com/server/scanengineupdate</Data>

  </EventData>

</Event>

I have checked also on a similar test environment and I get same error.

Solution to solve this issue is to give to "Network Service" account to have full control, or at least "write" access on \Program Files\Microsoft\Exchange Server\V15\FIP-FS\Data\Engines\amd64\Microsoft\bin .

After this change updates are working properly.