One in five British businesses has been hacked by cyber criminals in the past year, research has suggested.
Larger companies, defined as those with at least 100 staff, are more susceptible to cyber attacks, according to the survey of 1,200 businesses by the British Chambers of Commerce (BCC).
Its report found 42% of big businesses had fallen victim to cyber crime, compared with 18% of small companies.
Only a quarter (24%) of respondents said their business had security measures in place to guard against hacking.
Adam Marshall, BCC director-general, said: "Cyber attacks risk companies' finances, confidence and reputation, with victims reporting not only monetary losses, but costs from disruption to their business and productivity.
"While firms of all sizes, from major corporations to one-man operations, fall prey to attacks, our evidence shows that large companies are more likely to experience them.
"Firms need to be proactive about protecting themselves from cyber attacks.
"Security accreditations can help businesses assess their own IT infrastructure, defend against cyber-security breaches and mitigate the damage caused by an attack. It can also increase confidence among the businesses and clients who they engage with online.
"Businesses should also be mindful of the extension to data protection regulation coming into force next year, which will increase their responsibilities and requirements to protect personal data. Firms that don't adopt the appropriate protections leave themselves open to tough penalties.
"Companies are reporting a reliance on IT support providers to resolve cyber-attacks.
"More guidance from government and police about where and how to report attacks would provide businesses with a clear path to follow in the event of a cyber-security breach and increase clarity around the response options available to victims, which would help minimise the occurrence of cyber crime."
Web giant Yahoo, telecoms firm TalkTalk and controversial dating website Ashley Madison are among the high-profile businesses to have been subject to cyber attacks in recent years.
A Government spokesman said: "We are investing £1.9 billion to make the UK the safest place to live and do business online and recently established the National Cyber Security Centre to work with industry to protect the UK from cyber attacks.
"It's essential businesses take responsibility for their cyber security risks and we urge them to take advantage of our free advice, online training and Cyber Essentials scheme to protect against attacks."