IP addresses and the Data Protection Act
This guide is based on UK law. It was written in March
2007.
An IP address in isolation is not personal data under the Data
Protection Act, according to the Information Commissioner. But an
IP address can become personal data when combined with other
information or when used to build a profile of an individual, even
if that individual's name is unknown.
What is an IP address?
Computers and other devices that are connected to the internet
are assigned unique identifiers known as Internet Protocol (IP)
addresses to identify and communicate with each other.
The internet's authority for names and numbers is ICANN, based
in California. It delegates authority for the management and
creation of IP addresses to a body called the Internet Assigned
Numbers Authority (IANA). IANA allocates blocks of addresses to one
of five Regional Internet Registries, including RIPE in Europe. In
turn, these regional bodies allocate smaller blocks of addresses to
ISPs and organisations.
The most common type of IP address is displayed as four numbers
between zero and 255, e.g. 83.29.144.255. This format – known as IP
version 4 – will accommodate a maximum of 4.3 billion addresses.
The growing number of devices connected to the internet is driving
the adoption of IP version 6 – a format that will accommodate more
devices (it displays an IP address as eight groups of four
hexadecimal digits, e.g. 2001:0db8:0000:0000:0000:0000:1428:57ab),
though it is not yet widely supported.
When an individual connects his computer to the internet it is
either with the same IP address each time, known as a static IP
address; or with a different number each time, known as a dynamic
IP address. Some ISPs allocate dynamic IP addresses, others
allocate static IP addresses. Visiting an IP lookup
site will tell you what IP address you are currently
using. You can determine whether it is dynamic or static if you
disconnect your internet connection, reconnect and then check your
IP address again.
What can be determined from an IP address?
As soon as you visit a website your IP address will be available
to that site. It is common for websites to keep a record of all IP
addresses that visited with the data and time of the visit, even if
this record is never used. Your ISP also has a record of your
internet activity. Even if your IP address is a dynamic address –
i.e. it changes every time you connect to the internet – your ISP
will be able to identify your browsing activity because it knows
what number was allocated to which customer and when.
Limited information is freely available about any IP address.
Because IP addresses are allocated in batches, your IP address, be
it static or dynamic, will be in a particular range that typically
reveals your choice of ISP and your geographic location – though at
best this will identify a city, not a street, and it won't always
identify the right city or even the right country, depending on
your ISP and its system for allocating IP addresses.
When accessing a website from an office computer, you might
share one IP address with numerous colleagues. It is likely that
your office can identify which computer on its network accessed a
particular site, though, even if that site's access records show a
shared IP address.
Data protection and IP addresses
The Data Protection Act regulates the collection and use of
personal data. If data is not personal data it is not caught by the
Act – but it is not always obvious whether data is personal data or
not. An IP address in isolation is not personal data because it is
focused on a computer and not an individual. This reasoning was
applied by the Hong Kong Privacy Commissioner in a complaint about
Yahoo!'s disclosure of information about a journalist to Chinese
authorities (Hong Kong clears Yahoo! of
privacy breach over jailed journalist, OUT-LAW News,
15/03/2007). The Commissioner wrote in his report: "an IP address
per se does not meet the definition of 'personal data'".
In the hands of an ISP an IP address becomes personal data when
combined with other information that is held – which will include a
customer's name and address. In the hands of a website operator, it
can become personal data through user profiling.
Most sites do not profile their users using IP addresses. They
typically use IP addresses for demographic purposes such as
counting visitors, their countries of origin and their choice of
ISP. Their organisation might also be identifiable.
Sites typically gather statistical data about the path that
users take through a website and the page from which they left the
site. Banking websites might also use IP addresses as a security
measure – for example, if a customer regularly accesses his account
from an IP address in London, access to that customer's account
from an IP address in Moscow might indicate fraud.
The most common privacy concern surrounding IP addresses is
their use in marketing. A visitor's path through a website could be
followed and any adverts that are clicked can be identified. On the
next visit, that user could be shown ads that are similar to those
he clicked on the previous visit. But this fails when the user has
a dynamic IP address: the user will be unknown.
Accordingly, most websites prefer to use cookies to track users
for personalised marketing purposes in preference to IP addresses.
A cookie is a small text file that is sent from a website to a
visitor's computer. The cookie file can be used to identify an
individual and a website operator can build a detailed profile of
that person's activity at its site. Users can set their web
browsers to refuse cookies but most users accept them, often
unwittingly.
The Commissioner on IP addresses
In 2001, the then Information Commissioner, Elizabeth France,
acknowledged the difficulty of using IP addresses to build up
personalised profiles. "It is hard to see how the collection of
dynamic IP addresses without other identifying information would
bring a website operator within the scope of the Data Protection
Act 1998," she wrote.
She continued: "Static IP addresses are different. As with
cookies they can be linked to a particular computer which may
actually or by assumption be linked to an individual user. If
static IP addresses were to form the basis for profiles that are
used to deliver targeted marketing messages to particular
individuals they, and the profiles, would be personal data subject
to the Data Protection Act 1998. However, it is not easy for a
website operator to distinguish between dynamic and static IP
addresses. Thus the scope for using IP addresses for personalised
profiling is limited."
France concluded: "If dynamic or static IP addresses are
collected simply to analyse aggregate patterns of website use they
are not necessarily personal data. They will only become personal
data if the website operator has some means of linking IP addresses
to a particular individual, perhaps through other information held
or from information that is publicly available on the internet.
ISPs will of course be able to make this link but the information
they keep will not normally be available to a website
operator."
Similar guidance came from an independent EU advisory body
called the Article 29 Data Protection Working Party. It wrote in
November 2000: "The possibility exists in many cases, however, of
linking the user’s IP address to other personal data (which is
publicly available or not) that identify him/her, especially if use
is made of invisible processing means to collect additional data on
the user (for instance, using cookies containing a unique
identifier) or modern data mining systems linked to large databases
containing personally-identifiable data on internet users."
How this affects your web operations
If you collect IP addresses and analyse them
collectively – e.g. identifying the number of visitors from Japan
or the most popular ISP – you should disclose this in your privacy
policy, e.g. "When you visit our site we may automatically log your
IP address, a unique identifier for your computer or other access
device." To reassure visitors, you could add: "We will not use your
IP address to identify you in any way."
If you wish to use IP addresses to identify or build a profile
on each of your visitors as an individual, even if they are never
identified by name, you should assume that the Data Protection Act
applies. Only a court can decide for certain whether or not this is
a processing of personal data to which the Act applies and there
have been no court rulings on this point to date. The safest course
is to assume that the Act does apply in these circumstances. A
court will be influenced by the Information Commissioner's guidance
on this point. Therefore you should make visitors aware of your
intentions to use IP addresses and, where possible, gain consent
before processing an IP address for these
purposes, for example, via a data protection notice.
Links:
EU Data Protection Working Party Guidance (99-page / 510KB
PDF)
Please note: The UK Commissioner's guidance
appeared in a set of Website FAQ published in 2001 and no longer
available at the Commissioner's site.
Contacts: Louise Townsend or Rosemary Jay (Manchester, 0161 250 0100)
