An investigation by Which? found that hackers could access the provider’s Super Hub 2 router, allowing access to users’ smart appliances.
A child’s toy and domestic CCTV cameras were among the vulnerable devices.
Virgin Media said the risk was small but advised customers using default network and router passwords to update them immediately.
The company said the issue existed with other routers of the same age and was not exclusive to their model.
The study, carried out in conjunction with ethical security researchers SureCloud, tested 15 devices -of which eight had security flaws.
In one case a home CCTV system was hacked using an administrator account that was not password protected. Hackers were able to watch live pictures and in some cases were able to move cameras inside the house.