Nearly half of all UK businesses suffered a cyber breach or attack in the last year, an official survey reveals.
The Government study lays bare the growing threat from IT attacks as firms are targeted every day with potential losses running to millions of pounds.
Researchers found just under half (46%) of businesses identified at least one cyber security breach or attack in the previous 12 months.
This rises to two-thirds among medium-sized (66%) and large companies (68%).
Among all the businesses that detected breaches in the last year, they resulted in an average cost of £1,570.
This was much higher for the average large firm, at just under £20,000.
The most common breaches or attacks involved fraudulent emails, for example by coaxing staff into revealing passwords or financial information, or opening dangerous attachments, followed by viruses and malware.
Of the businesses which identified a breach or attack, almost a quarter had a temporary loss of files, a fifth had software or systems corrupted, one in 10 lost access to third party systems they rely on, and one in 10 had their website taken down or slowed.
The study also found firms holding electronic personal data on customers were much more likely to suffer cyber breaches than those that do not.
The 2017 Cyber Security Breaches Survey said there is an "increasing prioritisation" of cyber security, and more businesses have attempted to identify the risks they face.
Three quarters of all firms say the issue is a high priority for senior managers and directors and nine in 10 businesses regularly update their software and malware protection.
The report says: "While breaches do not always result in a material outcome, such as loss of data or network access, in cases where this does happen, it has a significant impact on the organisation.
"The survey finds that these organisations can also face considerable financial costs from breaches, not just in terms of the direct results of the breach and recovery or repair costs, but also in terms of the long-term damage to the business's reputation, among customers or investors."
Web giant Yahoo and telecoms firm TalkTalk are among the major organisations hit by cyber attacks in recent years.
Ciaran Martin, chief executive of the National Cyber Security Centre, said: "UK businesses must treat cyber security as a top priority if they want to take advantage of the opportunities offered by the UK's vibrant digital economy.
"The majority of successful cyber attacks are not that sophisticated but can cause serious commercial damage.
"By getting the basic defences right, businesses of every size can protect their reputation, finances and operating capabilities."
Liberal Democrat home affairs spokesman Brian Paddick said: "Cyber attacks present a serious and increasing threat to businesses requiring a concerted and international response.
"Businesses and the police need the training and knowledge to deal with these attacks. The Government must not shirk its duty just because this is happening online."