A marketplace security method implemented by a cloud service provider , the method comprising: registering (S280) a virtual machine, VM, service provider with a marketplace of the cloud service provider as a vendor; registering (S370) a VM image provided by the VM service provider with the marketplace ; downloading (S435) the VM image selected by a cloud service customer from the marketplace into a cloud space of the cloud service customer; obtaining an electronic signature associated with the downloaded VM image in response to an operation request (S445) of the cloud service customer; verifying (S450) the obtained electronic signature; and in case the electronic signature is successfully verified, operating a VM instance corresponding to the downloaded VM image in the cloud space of the cloud service customer, wherein the downloading (S435) comprises: in response to a download request from the cloud service customer, identifying the VM service provider that provides the VM image selected by the cloud service customer; detecting an authentication certificate issued from a certificate authority and obtained from the identified VM service provider in the vendor registration process or the registration process of the VM image; verifying the detected authentication certificate; and in case the authentication certificate is successfully verified (S425), downloading the selected VM image from the marketplace . registering (S280) a virtual machine, VM, service provider with a marketplace of the cloud service provider as a vendor; registering (S370) a VM image provided by the VM service provider with the marketplace ; downloading (S435) the VM image selected by a cloud service customer from the marketplace into a cloud space of the cloud service customer; obtaining an electronic signature associated with the downloaded VM image in response to an operation request (S445) of the cloud service customer; verifying (S450) the obtained electronic signature; and in case the electronic signature is successfully verified, operating a VM instance corresponding to the downloaded VM image in the cloud space of the cloud service customer, wherein the downloading (S435) comprises: in response to a download request from the cloud service customer, identifying the VM service provider that provides the VM image selected by the cloud service customer; detecting an authentication certificate issued from a certificate authority and obtained from the identified VM service provider in the vendor registration process or the registration process of the VM image; verifying the detected authentication certificate; and in case the authentication certificate is successfully verified (S425), downloading the selected VM image from the marketplace . in response to a download request from the cloud service customer, identifying the VM service provider that provides the VM image selected by the cloud service customer; detecting an authentication certificate issued from a certificate authority and obtained from the identified VM service provider in the vendor registration process or the registration process of the VM image; verifying the detected authentication certificate; and in case the authentication certificate is successfully verified (S425), downloading the selected VM image from the marketplace . <EOS>