The Syrian Electronic Army claimed that it gained access to both eBay and PayPal websites on Saturday.
Jarno Limnell, director of cyber security at Stonesoft said that this attack shows how wary large organisations now need to be.
"Cyberspace is increasingly being seen as an essential aspect of modern conflict. Large organisations, particularly financial ones, are perfect high-profile targets for hackers, such as the SEA, to garner attention and amplify their cause," he said.
"Because of threats like this, security teams within all industries need to assess their current protection, deploy appropriate measures and ensure employees are aware of the risks their firms face and remain vigilant."
While no customer data was accessed and no customer accounts were affected, the attack on two such high-profile sites sparked concern amongst users.
eBay and PayPal users in Europe and India trying to access the website on Saturday were met with a message from the hacktivist group criticising the companies' policy on denying online payments to Syrian customers.
"If your Paypal account is down for a few minutes, think about Syrians who were denied online payments for more than [three] years," the group posted on its Twitter account.
Screenshots of the defaced PayPal website were also uploaded to the SEA's twitter account as proof of the breach, but the account has since been suspended.
"For a brief period [on Saturday], a very limited number of people visiting certain Paypal and eBay marketing pages in the UK, France and India were redirected. The issue was quickly detected and resolved," said a spokesperson for eBay.
"We take the security and privacy of our customers very seriously and are actively investigating the reasons behind the temporary redirects."