Security questionnaires arrive in three broad shapes. Some buyers send the Shared Assessments SIG. Some ask for the Cloud Security Alliance's CAIQ. Many send a spreadsheet their own security team wrote, sometimes on top of one of the other two.
They cover much of the same ground, but they are not interchangeable. Each was built for a different kind of buyer, and each is read differently once you send it back. Treating them as one thing leads to answers that are technically accurate and still trigger a round of follow-up questions.
This article compares the three by origin, structure and use, then settles the practical question: whether to complete a standard questionnaire before anyone asks for it.
Where each one comes from
The SIG
SIG stands for Standardized Information Gathering. It is published by Shared Assessments, a membership organization focused on third-party risk management, and it is updated periodically. It was designed for outsourcing relationships in general, not only cloud services, so it covers areas like physical security, human resources and business resiliency alongside technical controls.
The SIG is common among buyers with mature third-party risk programs, financial institutions in particular. It comes in a shorter and a fuller form, usually called SIG Lite and SIG Core, and the requester is expected to scope it to the relationship rather than send every question to every vendor.
The CAIQ
CAIQ stands for Consensus Assessments Initiative Questionnaire. It is published by the Cloud Security Alliance (CSA) and derived from the CSA's Cloud Controls Matrix, a control framework written for cloud services. Each question traces to a control in the matrix, and the matrix itself is mapped to other standards such as ISO 27001.
Because it was written for cloud providers, the CAIQ leans heavily on questions about multi-tenancy, data isolation and how responsibility splits between provider and customer. A completed CAIQ can also be submitted to the CSA's STAR Registry as a self-assessment, which makes it publicly visible.
The custom questionnaire
A custom questionnaire is whatever the buyer's team decided to ask. It usually reflects their internal control standard, their regulator's expectations, and whatever went wrong with a vendor last year. It may arrive as a spreadsheet, a form in a vendor risk portal, or a document with free-text boxes.
Sector-specific standard questionnaires also exist, such as the HECVAT used by many higher education institutions. Treat those as standard formats with a narrower audience.
How they differ in practice
| SIG | CAIQ | Custom | |
|---|---|---|---|
| Publisher | Shared Assessments | Cloud Security Alliance | The buyer |
| Built for | Any third-party relationship | Cloud service providers | The buyer's own risk model |
| Scoping | Requester selects content; shorter and fuller versions | Fixed question set tied to the control matrix | Whatever the author included |
| Answer style | Yes, no or not applicable, with comments and attachments | Yes, no or not applicable, with an explanation | Varies: free text, ratings, uploads |
| Public option | Shared directly, often under NDA | Can be published as a STAR self-assessment | Rarely reused |
| Reuse across buyers | High, if kept current | High, if kept current | Content reusable, format not |
The table hides one important difference. With the SIG and the CAIQ, you know the questions in advance and can prepare a reviewed answer set. With a custom questionnaire, you discover the questions when it lands, and some of them will be phrased in ways that do not match how you describe your own controls.
What the reviewer does with your answers
The format tells you something about how your answers will be read.
A SIG usually feeds a structured third-party risk process. The buyer may score responses, and a "no" on a question they consider important often generates a follow-up automatically, whatever your comment says. Your comments still matter, because the analyst reviewing the flagged item reads them, but the yes, no or not applicable value carries more weight than you might expect.
A CAIQ is often read by someone who knows the Cloud Controls Matrix and is checking coverage across its domains. Explanations are where you show the implementation: which systems, which mechanism, which evidence. A bare "yes" with an empty description field tells this reviewer very little.
A custom questionnaire is usually read line by line by a person comparing your answers to their own policy. The questions they care most about are often the ones that look oddly specific, because those reflect a requirement they must enforce. If a question asks whether you encrypt backups with keys held in a separate account, that is rarely idle curiosity.
Should you complete one before anyone asks
Often yes, but pick deliberately and accept the upkeep.
A current, reviewed SIG or CAIQ gives you something to offer when a buyer asks whether you have a standard response. Some buyers will accept one in place of their own questionnaire, or use it to cut their own down to the gaps. Others will not, because their process requires their own format. Either way, every answer you have already written makes the next questionnaire faster.
Choose based on who buys from you:
Mostly cloud-focused technology buyers. The CAIQ fits, because it speaks their language about tenancy and shared responsibility.
Financial services and other heavily regulated buyers. The SIG is more likely to be what their process expects.
A mixed customer base. Start with whichever format your recent buyers asked for most often, and reuse its answers for the other.
Two cautions apply. First, a completed questionnaire is a dated statement. One that is a year old and describes a tool you have since replaced does more harm than having none. Second, publishing a CAIQ to the STAR Registry makes your answers public. Read every answer as if a competitor and an attacker will both see it, because they can.
Answering a custom questionnaire without starting from zero
A custom questionnaire is mostly familiar questions in unfamiliar wording. A practical order of work:
Ask whether a standard response or report is acceptable. Offer your SIG or CAIQ, and your SOC 2 or ISO 27001 certificate if you have one. The answer is sometimes yes for part of the questionnaire.
Map each question to an answer you already have. Most will map. Mark the ones that do not.
Read the unmapped questions carefully. These are where the buyer's real concerns usually sit, and they deserve a considered answer rather than a rushed one.
Keep the meaning of your answer, change only the wording. If a question is phrased so that "yes" overstates your control, answer with the qualifier rather than bending the fact to fit the cell.
Record any new answer for reuse. The next buyer will ask the same thing in different words.
If you hold a certification or attestation, cite the relevant controls by reference. A reviewer who knows the SOC 2 trust services criteria or the ISO 27001 control set will often accept "covered by our report, see section X" for questions the report already answers.
Mistakes that cost the most time
These come up across all three formats:
Unqualified answers. "Yes" to a question about MFA when it is enforced for staff but optional for customers. The qualifier belongs in the comment.
"Not applicable" for inherited controls. Physical data center security applies to you even if your cloud provider operates it. The accurate answer says who operates the control and how you rely on it.
Empty comment fields. A reviewer cannot score what is not there, and will ask.
Answering an old version. Standard questionnaires change between releases. Check which version the buyer sent before reusing answers from another one.
Drift between formats. If your SIG says logs are kept for one period and your CAIQ says another, someone will notice. Keep one set of facts and derive both from it.
A next step
Pull the last few questionnaires you answered and sort them by format. If one standard questionnaire dominates, complete it properly, have the control owners review it, and date it. If most are custom, the investment is in the answers rather than any one format. The glossary entry on security questionnaires is a useful primer for colleagues in sales or legal.