Well, this is only partially true. The virus that causes cold sores is indeed called the herpes virus. But, it is not the same herpes virus that causes genital herpes, the sexually transmitted disease.
In general, cold sores are caused by herpes simplex virus type I or HSV-I. The other type of herpes virus is known as HSV-2.
In most people with cold sores, the virus is picked up during childhood and lies dormant for many years before re-activating later on in life.